MIPS/testsuite: add -mno-branch-likely to r10k-cache-barrier-13.c

In mips.cc(mips_reorg_process_insns), there is this claim:

    Also delete cache barriers if the last instruction
    was an annulled branch.  INSN will not be speculatively
    executed.

And with -O1 on mips64, we can generate binary code like this,
which fails this test.

gcc/testsuite
	* gcc.target/mips/r10k-cache-barrier-13.c: Add -mno-branch-likely
	option.