MIPS/LD/testsuite: Fix IRIX dumps for n64 GOT relocation tests

MIPS/LD/testsuite: Fix IRIX dumps for n64 GOT relocation tests

Factor in the presence of a `.gnu.attributes' section at the end of the
respective dumps:

Disassembly of section .gnu.attributes:

0000000000000000 <.gnu.attributes>:
   0:	41000000 	bc0f	4 <__dso_displacement+0x4>
   4:	0f676e75 	jal	d9db9d4 <__dso_displacement+0xd9db9d4>
   8:	00010000 	sll	zero,at,0x0
   c:	00070401 	0x70401

and also ignore any trailing output with the IRIX variant of n64 GOT
relocation tests, like already done with the Linux and the embedded
ones, removing:

FAIL: MIPS ELF got reloc n64
FAIL: MIPS ELF xgot reloc n64

LD testsuite regressions with the `mips-sgi-irix6' target.

	ld/
	* testsuite/ld-mips-elf/elf-rel-got-n64.d: Add `#pass' at the
	end.
	* testsuite/ld-mips-elf/elf-rel-xgot-n64.d: Likewise.