ArmPkg/ArmGicV3Dxe: Use ArmGicSetInterruptPriority() to set priority

ArmPkg/ArmGicV3Dxe: Use ArmGicSetInterruptPriority() to set priority

When Affinity Routing enabled, the GICR_IPRIORITYR<n> is used to set
priority for SGIs and PPIs instead of GICD_IPRIORITYR<n>.
This patch calls ArmGicSetInterruptPriority() helper function when
setting priority to handle the difference.

Cc: Leif Lindholm <leif@nuviainc.com>
Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
Reviewed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>