Revert "x86_64: Suppress false positive valgrind error"

This reverts commit a1735e0a.

The test failure is a real valgrind bug that needs to be fixed before
valgrind is usable with a glibc that has been built with
CC="gcc -march=x86-64-v3".  The proposed valgrind patch teaches
valgrind to replace ld.so strcmp with an unoptimized scalar
implementation, thus avoiding any AVX2-related problems.

Valgrind bug: <https://bugs.kde.org/show_bug.cgi?id=485487

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Reviewed-by: H.J. Lu <hjl.tools@gmail.com>