x86/apb: Fix configuration constraints

The APB timer requires SFI, SCU and MID support
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Link: http://lkml.kernel.org/r/20111217215719.3743.93550.stgit@bob.linux.org.ukSigned-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -665,6 +665,7 @@ config APB_TIMER
        def_bool y if MRST
        prompt "Langwell APB Timer Support" if X86_MRST
        select DW_APB_TIMER
+       depends on X86_INTEL_MID && SFI
        help
          APB timer is the replacement for 8254, HPET on X86 MID platforms.
          The APBT provides a stable time base on SMP