aarch64: Alter pr116258.c test to correct for big endian.

aarch64: Alter pr116258.c test to correct for big endian.

The test at pr116258.c fails on big endian targets,
this is because the test checks that the index of a floating
point multiply is 0, which is correct only for little endian.

gcc/testsuite/ChangeLog:

	PR tree-optimization/116258
	* gcc.target/aarch64/pr116258.c:
	Alter test to add big-endian support.