x86: move mmconfig declarations to header

arch/x86/kernel/mmconf-fam10h_64.c is missing the prototypes, which
are decalred in arch/x86/kernel/setup_64.c. Move the prototypes and
the inline stubs to the appropriate header file.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>