ArmPkg/ArmGic: Returned the InterruptId in ArmGicAcknowledgeInterrupt()

ArmPkg/ArmGic: Returned the InterruptId in ArmGicAcknowledgeInterrupt()

The InterruptId has a different width for GicV2 and GicV3 (respectively
10bit and 24bit).
The function prototype has been changed to return this value to make the
caller GIC architecture version independent. Otherwise, we would have need
to expose a different mask to allow the caller to retrieve this value from
the read register.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15628 6f19259b-4bc3-4df7-8a09-765794883524