Revert "KVM: x86: enable -Werror"

This reverts commit ead68df9.

Using the -Werror flag breaks the build for me due to mostly harmless
KASAN or similar warnings:

  arch/x86/kvm/x86.c: In function ‘kvm_timer_init’:
  arch/x86/kvm/x86.c:7209:1: error: the frame size of 1112 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Feel free to add a CONFIG_WERROR if you care strong enough, but don't
break peoples builds for absolutely no good reason.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>