x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK

All 486+ CPUs support WP in supervisor mode, so remove the fallback
386 support code.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1354132230-21854-7-git-send-email-hpa@linux.intel.com