More tests in gdb.arch/insn-reloc.c

More tests in gdb.arch/insn-reloc.c

This patch adds more tests in gdb.arch/insn-reloc.c to cover
instruction BL and cover B.CON when CON is false.  These new added
tests can be used for displaced stepping too.

gdb/testsuite:

2015-10-12  Yao Qi  <yao.qi@linaro.org>

	* gdb.arch/insn-reloc.c (can_relocate_bcond): Rename to ...
	(can_relocate_bcond_true): ... it.
	(can_relocate_bcond_false): New function.
	(foo): Likewise.
	(can_relocate_bl): Likewise.
	(testcases) [__aarch64__]: Add can_relocate_bcond_false and
	can_relocate_bl.