feat: specify virtual interrupt count per vCPU

Currently, in hafnium, vitual interrupt ID is tied to physical
interrupt ID. This limitation in design limits the max physical
secure interrupt that can be handled by SPMC. Hence, the number of
virtual interrupts supported for each vCPU by FVP and QEMU SPMC builds
is increased to 1024 to match the maximum number of physical
interrupts supported by GICv3 IP(excluding extended INTID range).

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I2fc58c345c6f3d09acb1ffc91e710a0d493f4924