x86: add include to cpu/intel.c

Fixes sparse warning:

arch/x86/kernel/cpu/intel.c:48:15: warning: symbol 'ppro_with_ram_bug' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>