x86: build fix

fix:

arch/x86/kernel/setup_32.c:409: error: 'enable_local_apic' undeclared (first use in this function)
arch/x86/kernel/setup_32.c:409: error: (Each undeclared identifier is reported only once
arch/x86/kernel/setup_32.c:409: error: for each function it appears in.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>