testsuite: Avoid strict aliasing violations in some avx512 tests

testsuite: Avoid strict aliasing violations in some avx512 tests

These tests violated strict aliasing, fixed by using a union and
type punning through that.

2020-12-08  Jakub Jelinek  <jakub@redhat.com>

	* gcc.target/i386/avx512dq-vandnpd-2.c (CALC): Use union
	to avoid aliasing violations.
	* gcc.target/i386/avx512dq-vandnps-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vandpd-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vandps-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vorpd-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vorps-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vxorpd-2.c (CALC): Likewise.
	* gcc.target/i386/avx512dq-vxorps-2.c (CALC): Likewise.