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/Makefile b/arch/arm/mach-stm32mp/Makefile
index 0ffec6e..1db9057 100644
--- a/arch/arm/mach-stm32mp/Makefile
+++ b/arch/arm/mach-stm32mp/Makefile
@@ -8,6 +8,7 @@
 obj-y += syscon.o
 obj-y += bsec.o
 
+obj-$(CONFIG_STM32MP13x) += stm32mp13x.o
 obj-$(CONFIG_STM32MP15x) += stm32mp15x.o
 
 ifdef CONFIG_SPL_BUILD