x86: MTRR workaround for system with stange var MTRRs

Impact: don't trim e820 according to wrong mtrr

Ozan reports that his server emits strange warning.
it turns out the BIOS sets the MTRRs incorrectly.

Ignore those strange ranges, and don't trim e820,
just emit one warning about BIOS

Reported-by: Ozan Çağlayan <ozan@pardus.org.tr>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <49BEE1E7.7020706@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>