xen/arm: Use the new functions for vCPUID/vaffinity transformation

xen/arm: Use the new functions for vCPUID/vaffinity transformation

There are 3 places to change:

* Initialise vMPIDR value in vcpu_initialise()
* Find the vCPU from vMPIDR affinity information when accessing GICD
  registers in vGIC
* Find the vCPU from vMPIDR affinity information when booting with vPSCI
  in vGIC
  - Both PSCI 0.1 and PSCI 0.2 are modified to respect the MPIDR like.

Signed-off-by: Chen Baozi <baozich@gmail.com>
Reviewed-by: Julien Grall <julien.grall@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>