Fix pointer type mismatch of handlers

Commit 4c0d03907652 ("Rework type usage in Trusted Firmware") changed
the type usage in struct declarations, but did not touch the definition
side.  Fix the type mismatch.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/drivers/arm/gic/gic_v3.c b/drivers/arm/gic/gic_v3.c
index 3e802fd..5486817 100644
--- a/drivers/arm/gic/gic_v3.c
+++ b/drivers/arm/gic/gic_v3.c
@@ -8,7 +8,7 @@
 #include <debug.h>
 #include <gic_v3.h>
 
-uintptr_t gicv3_get_rdist(uintptr_t gicr_base, uint64_t mpidr)
+uintptr_t gicv3_get_rdist(uintptr_t gicr_base, u_register_t mpidr)
 {
 	uint32_t  cpu_aff, gicr_aff;
 	uint64_t  gicr_typer;