refactor(st): move GIC code to common directory

The GIC v2 initialization code could be shared to other ST platforms.
The stm32mp1_gic.c file is then moved to common directory, and renamed
stm32mp_gic.c.
The functions are also prefixed with stm32mp_gic.

Change-Id: I60820823b470217d3a95cc569f941c2cb923dfa9
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/plat/st/stm32mp1/sp_min/sp_min-stm32mp1.mk b/plat/st/stm32mp1/sp_min/sp_min-stm32mp1.mk
index 1d754d9..f5184e7 100644
--- a/plat/st/stm32mp1/sp_min/sp_min-stm32mp1.mk
+++ b/plat/st/stm32mp1/sp_min/sp_min-stm32mp1.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2017-2022, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2017-2023, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -32,7 +32,7 @@
 
 BL32_SOURCES		+=	${GICV2_SOURCES}			\
 				plat/common/plat_gicv2.c		\
-				plat/st/stm32mp1/stm32mp1_gic.c
+				plat/st/common/stm32mp_gic.c
 
 # Generic PSCI
 BL32_SOURCES		+=	plat/common/plat_psci_common.c