testsuite/i386: Require AVX2 effective target in pr107432-9.c

x86-64-v3 requires AVX2 effective target and AVX2 specific avx2-check.h.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr107432-9.c: Require AVX2 effective target.
	Include avx2-check.h instead of avx-check.h.  Define TEST to avx2_test.