MIPS/LD/testsuite: Correct comm-data.exp test ABI/emul/endian arrangement

MIPS/LD/testsuite: Correct comm-data.exp test ABI/emul/endian arrangement

Update the ld-mips-elf/comm-data.exp test script to correctly select
emulations for targets using non-traditional MIPS emulation and also
correctly select ABIs for targets that do not support all of them, and
finally use the default endianness selection to benefit targets which
support only one, complementing commit 05a5feafdd38 ("Rewrite
check_shared_lib_support") and removing numerous test failures such as:

FAIL: MIPS o32/copyreloc common symbol override test (auxiliary shared object build)
FAIL: MIPS o32/copyreloc common symbol override test
FAIL: MIPS o32/nocopyreloc common symbol override test (auxiliary shared objectbuild)
FAIL: MIPS o32/nocopyreloc common symbol override test
FAIL: MIPS n32/copyreloc common symbol override test (auxiliary shared object build)
FAIL: MIPS n32/copyreloc common symbol override test
FAIL: MIPS n32/nocopyreloc common symbol override test (auxiliary shared objectbuild)
FAIL: MIPS n32/nocopyreloc common symbol override test

due to:

.../ld/ld-new: unrecognised emulation mode: elf32btsmip
Supported emulations: elf64btsmip elf64ltsmip

or:

.../ld/ld-new: unrecognised emulation mode: elf32btsmip
Supported emulations: elf32ebmip

or:

.../ld/ld-new: unrecognised emulation mode: elf32btsmip
Supported emulations: elf32l4300

etc., and:

ERROR: -n32 -march=mips3 -EB -call_shared .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data1.s: assembly failed
UNRESOLVED: MIPS n32/copyreloc common symbol override test (auxiliary shared object build)
ERROR: -n32 -march=mips3 -EB -call_nonpic .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data2.s: assembly failed
UNRESOLVED: MIPS n32/copyreloc common symbol override test
ERROR: -n32 -march=mips3 -EB -call_shared .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data1.s: assembly failed
UNRESOLVED: MIPS n32/nocopyreloc common symbol override test (auxiliary shared object build)
ERROR: -n32 -march=mips3 -EB -call_nonpic .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data2.s: assembly failed
UNRESOLVED: MIPS n32/nocopyreloc common symbol override test

due to:

Assembler messages:
Fatal error: selected target format 'elf32-nbigmips' unknown

and:

ERROR: -64 -march=mips3 -EB -call_shared .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data1.s: assembly failed
UNRESOLVED: MIPS n64/copyreloc common symbol override test (auxiliary shared object build)
ERROR: -64 -march=mips3 -EB --defsym ELF64=1 -call_nonpic .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data2.s:assembly failed
UNRESOLVED: MIPS n64/copyreloc common symbol override test
ERROR: -64 -march=mips3 -EB -call_shared .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data1.s: assembly failed
UNRESOLVED: MIPS n64/nocopyreloc common symbol override test (auxiliary shared object build)
ERROR: -64 -march=mips3 -EB --defsym ELF64=1 -call_nonpic .../ld/testsuite/ld-mips-elf/../ld-elf/comm-data2.s:assembly failed
UNRESOLVED: MIPS n64/nocopyreloc common symbol override test

due to:

Assembler messages:
Fatal error: no compiled in support for 64 bit object file format

	ld/
	* testsuite/ld-mips-elf/comm-data.exp: Correct support for
	targets using non-traditional MIPS emulation or having a limited
	selection of ABIs available.  Don't force big endianness, use
	defaults.