ArmPkg: Tidy GIC code before changes.

This change is purely cosmetic, to tidy some code before change.
Mods involve:
    Re-order #includes
    Reformat comments.
    Use ns consistently (always "100ns" not sometimes "100 nS")
    Split overlength code lines.
    Make protocol functions STATIC.
    Remove "Horor vacui" comments.
    Rationalize GIC register address calculations
    Replace explicit test and assert with ASSERT_EFI_ERROR.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Girish Pathak <girish.pathak@arm.com>
Signed-off-by: Alexei Fedorov <alexei.fedorov@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

ArmPkg/Drivers/ArmGic/ArmGicDxe.h

@@ -1,6 +1,6 @@
 /*++
 
-Copyright (c) 2013-2014, ARM Ltd. All rights reserved.<BR>
+Copyright (c) 2013-2017, ARM Ltd. All rights reserved.<BR>
 
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
@@ -28,9 +28,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 extern UINTN                        mGicNumInterrupts;
 extern HARDWARE_INTERRUPT_HANDLER  *gRegisteredInterruptHandlers;
 
-//
 // Common API
-//
 EFI_STATUS
 InstallAndRegisterInterruptService (
   IN EFI_HARDWARE_INTERRUPT_PROTOCOL   *InterruptProtocol,
@@ -46,18 +44,14 @@ RegisterInterruptSource (
   IN HARDWARE_INTERRUPT_HANDLER         Handler
   );
 
-//
 // GicV2 API
-//
 EFI_STATUS
 GicV2DxeInitialize (
   IN EFI_HANDLE         ImageHandle,
   IN EFI_SYSTEM_TABLE   *SystemTable
   );
 
-//
 // GicV3 API
-//
 EFI_STATUS
 GicV3DxeInitialize (
   IN EFI_HANDLE         ImageHandle,