x86: wrap MCA_bus test around an ifdef

Only test for MCA_bus if support for MCA is compiled in.
Also, for x86_64, write the code inside the conditional
for consistency with i386. It won't bite us, since it'll
probably never select CONFIG_MCA anyway.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/time_32.c

@@ -94,6 +94,7 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
 
 	do_timer_interrupt_hook();
 
+#ifdef CONFIG_MCA
 	if (MCA_bus) {
 		/* The PS/2 uses level-triggered interrupts.  You can't
 		turn them off, nor would you want to (any attempt to
@@ -107,6 +108,7 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
 		u8 irq_v = inb_p( 0x61 );	/* read the current state */
 		outb_p( irq_v|0x80, 0x61 );	/* reset the IRQ */
 	}
+#endif
 
 	return IRQ_HANDLED;
 }