x86, 386 removal: Remove CONFIG_INVLPG

All 486+ CPUs support INVLPG, so remove the fallback 386 support
code.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1354132230-21854-6-git-send-email-hpa@linux.intel.com