testsuite: fix ASAN errors in i386.exp tests
gcc/testsuite/ChangeLog:
* gcc.target/i386/avx2-i32gatherpd256-4.c: Fix ASAN errors.
* gcc.target/i386/avx2-i32gatherq256-4.c: Likewise.
* gcc.target/i386/avx2-i64gatherpd256-4.c: Likewise.
* gcc.target/i386/avx2-i64gatherq256-4.c: Likewise.
* gcc.target/i386/avx2-vpabsb256-2.c: Likewise.
* gcc.target/i386/avx2-vpabsd256-2.c: Likewise.
* gcc.target/i386/avx2-vpabsw256-2.c: Likewise.
* gcc.target/i386/avx256-unaligned-load-7.c: Likewise.
* gcc.target/i386/avx256-unaligned-store-7.c: Likewise.
* gcc.target/i386/pr64291-1.c: Likewise.