KVM: arm64: Slightly optimize flush_context()

bitmap_zero() is faster than bitmap_clear(), so use it to save a few
cycles.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/97bf2743f3a302b3066aced02218b9da60690dd3.1681854412.git.christophe.jaillet@wanadoo.fr

arch/arm64/kvm/vmid.c

@@ -47,7 +47,7 @@ static void flush_context(void)
 	int cpu;
 	u64 vmid;
 
-	bitmap_clear(vmid_map, 0, NUM_USER_VMIDS);
+	bitmap_zero(vmid_map, NUM_USER_VMIDS);
 
 	for_each_possible_cpu(cpu) {
 		vmid = atomic64_xchg_relaxed(&per_cpu(active_vmids, cpu), 0);