x86: mce: Make CONFIG_X86_ANCIENT_MCE dependent on CONFIG_X86_MCE

Add a missing depency for ANCIENT_MCE. It didn't matter
in practice because the ANCIENT code wasn't compiled without
X86_MCE, but it's better to express that clearly in
Kconfig.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>