arm: stm32mp: add support of STM32MP13x

Introduce the code in mach-stm32mp and the configuration file
stm32mp13_defconfig for the new STM32MP family.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/cpu.c b/arch/arm/mach-stm32mp/cpu.c
index b808964..240960a 100644
--- a/arch/arm/mach-stm32mp/cpu.c
+++ b/arch/arm/mach-stm32mp/cpu.c
@@ -52,8 +52,11 @@
 	enum dcache_option option;
 
 	if (IS_ENABLED(CONFIG_SPL_BUILD)) {
+/* STM32_SYSRAM_BASE exist only when SPL is supported */
+#ifdef CONFIG_SPL
 		start = ALIGN_DOWN(STM32_SYSRAM_BASE, MMU_SECTION_SIZE);
 		size = ALIGN(STM32_SYSRAM_SIZE, MMU_SECTION_SIZE);
+#endif
 	} else if (gd->flags & GD_FLG_RELOC) {
 		/* bd->bi_dram is available only after relocation */
 		start = bd->bi_dram[bank].start;