aarch64: Fix up 2 other combine opt regressions vs. GCC8 [PR100075]

The testcase is endianness dependent and works only on little-endian.

2021-04-19  Christophe Lyon  <christophe.lyon@linaro.org>

	PR target/100075
	gcc/testsuite/
	* gcc.target/aarch64/pr100075.c: Add aarch64_little_endian
	effective target.