refactor(st): move boot backup register management

This backup register used to pass boot information to BL33, has the
same mapping for ST platforms. Its management can then be moved to
common directory.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Ic873f099c1f87c6ba2825b4946365ae6a9687798
diff --git a/plat/st/stm32mp1/stm32mp1_def.h b/plat/st/stm32mp1/stm32mp1_def.h
index f0d8526..8cac4b5 100644
--- a/plat/st/stm32mp1/stm32mp1_def.h
+++ b/plat/st/stm32mp1/stm32mp1_def.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2022, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2023, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -548,6 +548,7 @@
  ******************************************************************************/
 #define TAMP_BASE			U(0x5C00A000)
 #define TAMP_BKP_REGISTER_BASE		(TAMP_BASE + U(0x100))
+#define TAMP_BKP_REG_CLK		RTCAPB
 #define TAMP_COUNTR			U(0x40)
 
 #if !(defined(__LINKER__) || defined(__ASSEMBLER__))