MIPS/testsuite: Add -mno-abicalls option to unaligned-2.c

PIC/abicalls option will generate some GOT operation, and some
`ld/sd` instructions are used.

Let's skip them.

gcc/testsuite
	* gcc.target/mips/unaligned-2.c: Add -mno-abicalls option.

gcc/testsuite/gcc.target/mips/unaligned-2.c

-/* { dg-options "isa_rev>=6 -mgp64" } */
+/* { dg-options "isa_rev>=6 -mgp64 -mno-abicalls" } */
 /* { dg-skip-if "code quality test" { *-*-* } { "-O0" } { "" } } */
 /* { dg-final { scan-assembler-not "\tsb\t" } } */
 /* { dg-final { scan-assembler-not "\tsh\t" } } */