kvm/ppc/mpic: remove users

This is an unused (no pun intended) leftover from when this code did
reference counting.

Signed-off-by: Scott Wood <[e-mail]>
Signed-off-by: Alexander Graf <[e-mail]>

arch/powerpc/kvm/mpic.c

···
 	struct kvm_io_device mmio;
 	const struct mem_reg *mmio_regions[MAX_MMIO_REGIONS];
 	int num_mmio_regions;
-	atomic_t users;
 
 	gpa_t reg_base;
 	spinlock_t lock;