arm: vgic: Split vgic_domain_init() functionality into two functions

Separate the code logic that does the registration of vgic_v3/v2 ops
to a new function domain_vgic_register(). The intention of this
separation is to record the required mmio count in vgic_v3/v2_init()
and pass it to function domain_io_init() in a follow-up patch patch.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/vgic.c

@@ -90,19 +90,8 @@ static void vgic_rank_init(struct vgic_irq_rank *rank, uint8_t index,
         rank->vcpu[i] = vcpu;
 }
 
-int domain_vgic_init(struct domain *d, unsigned int nr_spis)
+static int domain_vgic_register(struct domain *d)
 {
-    int i;
-    int ret;
-
-    d->arch.vgic.ctlr = 0;
-
-    /* Limit the number of virtual SPIs supported to (1020 - 32) = 988  */
-    if ( nr_spis > (1020 - NR_LOCAL_IRQS) )
-        return -EINVAL;
-
-    d->arch.vgic.nr_spis = nr_spis;
-
     switch ( d->arch.vgic.version )
     {
 #ifdef CONFIG_HAS_GICV3
@@ -121,6 +110,26 @@ int domain_vgic_init(struct domain *d, unsigned int nr_spis)
         return -ENODEV;
     }
 
+    return 0;
+}
+
+int domain_vgic_init(struct domain *d, unsigned int nr_spis)
+{
+    int i;
+    int ret;
+
+    d->arch.vgic.ctlr = 0;
+
+    /* Limit the number of virtual SPIs supported to (1020 - 32) = 988  */
+    if ( nr_spis > (1020 - NR_LOCAL_IRQS) )
+        return -EINVAL;
+
+    d->arch.vgic.nr_spis = nr_spis;
+
+    ret = domain_vgic_register(d);
+    if ( ret < 0 )
+        return ret;
+
     spin_lock_init(&d->arch.vgic.lock);
 
     d->arch.vgic.shared_irqs =