stm32mp: limit size of cacheable DDR in pre-reloc stage

In pre-reloc stage, U-Boot marks cacheable the DDR limited by
the new config CONFIG_DDR_CACHEABLE_SIZE.

This patch allows to avoid any speculative access to DDR protected by
firewall and used by OP-TEE; the "no-map" reserved memory
node in DT are assumed after this limit:
STM32_DDR_BASE + DDR_CACHEABLE_SIZE.

Without security, in basic boot, the value is equal to STM32_DDR_SIZE.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/arch/arm/mach-stm32mp/cpu.c b/arch/arm/mach-stm32mp/cpu.c
index f19e5c3..6785ab6 100644
--- a/arch/arm/mach-stm32mp/cpu.c
+++ b/arch/arm/mach-stm32mp/cpu.c
@@ -230,7 +230,8 @@
 			round_up(STM32_SYSRAM_SIZE, MMU_SECTION_SIZE),
 			DCACHE_DEFAULT_OPTION);
 	else
-		mmu_set_region_dcache_behaviour(STM32_DDR_BASE, STM32_DDR_SIZE,
+		mmu_set_region_dcache_behaviour(STM32_DDR_BASE,
+						CONFIG_DDR_CACHEABLE_SIZE,
 						DCACHE_DEFAULT_OPTION);
 }