tools/x86/kcpuid: Remove unused variable

Global variable "num_leafs" is set in multiple places but is never read
anywhere.  Remove it.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240718134755.378115-2-darwi@linutronix.de