[AArch64] Fix strict aliasing issue in gcc.target/aarch64/simd/vminmaxnm_1.c

[AArch64] Fix strict aliasing issue in gcc.target/aarch64/simd/vminmaxnm_1.c

While doing some unrelated work the gcc.target/aarch64/simd/vminmaxnm_1.c testcase started failing for me.
Upon investigation it turns out that it breaks the C strict aliasing rules in the CHECK macro by casting
a pointer to an incompatible type and dereferencing it. GCC even warns about it if compiled with -Wstrict-aliasing.

This patch fixes the testcase by making it use memcmp to compare the vector elements.
This avoids the undefined behaviour.

The testcase still passes on trunk.

    * gcc.target/aarch64/simd/vminmaxnm_1.c: Fix strict aliasing issues.

From-SVN: r249972