x86: fix unconditional arch/x86/kernel/pcspeaker.o compiling

do not add the pcspkr platform device if pcspkr support is disabled.
Signed-off-by: Michael Opdenacker <michael@free-electrons.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/Makefile

@@ -67,7 +67,10 @@ obj-$(CONFIG_MGEODE_LX)		+= geode_32.o mfgpt_32.o
 
 obj-$(CONFIG_VMI)		+= vmi_32.o vmiclock_32.o
 obj-$(CONFIG_PARAVIRT)		+= paravirt.o paravirt_patch_$(BITS).o
+
+ifdef CONFIG_INPUT_PCSPKR
 obj-y				+= pcspeaker.o
+endif
 
 obj-$(CONFIG_SCx200)		+= scx200_32.o