arm/vgic: Change fixed number of mmio handlers to variable number

arm/vgic: Change fixed number of mmio handlers to variable number

Compute the number of mmio handlers that are required for vGICv3 and
vGICv2 emulation drivers in vgic_v3_init()/vgic_v2_init(). Augment
this variable number of mmio handlers to a fixed number MAX_IO_HANDLER
and pass it to domain_io_init() to allocate enough memory.

New code path:
 domain_vgic_register(&count)
   domain_io_init(count + MAX_IO_HANDLER)
     domain_vgic_init()

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