KVM: arm64: Refactor kvm_arm_num_regs() for easier maintenance

kvm_arm_num_regs() adds together various partial register counts in
a freeform sum expression, which makes it harder than necessary to
read diffs that add, modify or remove a single term in the sum
(which is expected to the common case under maintenance).

This patch refactors the code to add the term one per line, for
maximum readability.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/guest.c

@@ -258,8 +258,14 @@ static int get_timer_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
  */
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
 {
-	return num_core_regs() + kvm_arm_num_sys_reg_descs(vcpu)
-		+ kvm_arm_get_fw_num_regs(vcpu)	+ NUM_TIMER_REGS;
+	unsigned long res = 0;
+
+	res += num_core_regs();
+	res += kvm_arm_num_sys_reg_descs(vcpu);
+	res += kvm_arm_get_fw_num_regs(vcpu);
+	res += NUM_TIMER_REGS;
+
+	return res;
 }
 
 /**