x86: fix section mismatch warning in acpi/boot.c

Fix following warning:
WARNING: arch/x86/kernel/built-in.o(.text+0x10ea0): Section mismatch: reference to .cpuinit.data:num_processors in 'acpi_unmap_lsapic'

The exported function acpi_unmap_lsapic() references
the variable num_processors that is annotated __cpuinitdata.

Remove the annotation of num_processors as we never know
when an exported function are called.
And drop the needless initialsation to 0.

Warning was seen on 64 bit but similar pattern were seen
in 32 bit - so fix it up there too.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>