x86: visws_quirks, fix build error

fix:

 arch/x86/kernel/visws_quirks.c: In function ‘visws_early_detect’:
 arch/x86/kernel/visws_quirks.c:290: error: ‘skip_ioapic_setup’ undeclared (first use in this function)
 arch/x86/kernel/visws_quirks.c:290: error: (Each undeclared identifier is reported only once
 arch/x86/kernel/visws_quirks.c:290: error: for each function it appears in.)

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