refactor(st-ddr): reorganize generic and specific elements

stm32mp_ddrctl structure contains DDRCTRL registers definitions.
stm32mp_ddr_info contains general DDR information extracted from DT.
stm32mp_ddr_size moves to the generic side.
stm32mp1_ddr_priv contains platform private data.

stm32mp_ddr_dt_get_info() and stm32mp_ddr_dt_get_param() allow to
retrieve data from DT. They are located in new generic c/h files in
which stm32mp_ddr_param structure is declared. Platform makefile
is updated.

Adapt driver with this new classification.

Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>
Change-Id: I4187376c9fff1a30e7a94407d188391547107997
diff --git a/plat/st/stm32mp1/stm32mp1_def.h b/plat/st/stm32mp1/stm32mp1_def.h
index b43245f..9527469 100644
--- a/plat/st/stm32mp1/stm32mp1_def.h
+++ b/plat/st/stm32mp1/stm32mp1_def.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -472,6 +472,7 @@
  * Device Tree defines
  ******************************************************************************/
 #define DT_BSEC_COMPAT			"st,stm32mp15-bsec"
+#define DT_DDR_COMPAT			"st,stm32mp1-ddr"
 #define DT_IWDG_COMPAT			"st,stm32mp1-iwdg"
 #define DT_PWR_COMPAT			"st,stm32mp1,pwr-reg"
 #define DT_RCC_CLK_COMPAT		"st,stm32mp1-rcc"