smp: Make __smp_processor_id() 0-argument macro

smp_processor_id family of macros never accepted any arguments.

	#define __smp_processor_id(x)

works by accident (see C99 6.10.3 §4). __smp_processor_id() gets
1 (empty) argument and passes it down to raw_smp_processor_id()
which doesn't accept arguments.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/0037d1f2-8153-4b33-b43e-f4b6ecd710ac@p183