refactor(fvp): use more arm generic code for gicv3

The arm generic implementation for the GIC is quite comprehensive and
the fvp's requirements don't diverge too much. Despite that, they
completely override a lot of code that is effectively reused. Use the
generic implementation instead to make it easier to follow and override
as little code as possible.

Change-Id: I3474aa970d7fbb91d75c0be6a255bc0da734f860
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/plat/arm/common/arm_gicv3.c b/plat/arm/common/arm_gicv3.c
index 5becbcd..180da2f 100644
--- a/plat/arm/common/arm_gicv3.c
+++ b/plat/arm/common/arm_gicv3.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2025, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -79,7 +79,7 @@
 	return plat_arm_calc_core_pos(mpidr);
 }
 
-static const gicv3_driver_data_t arm_gic_data __unused = {
+gicv3_driver_data_t arm_gic_data __unused = {
 	.gicd_base = PLAT_ARM_GICD_BASE,
 	.gicr_base = 0U,
 	.interrupt_props = arm_interrupt_props,