arm: Rename STM32MP13x

CONFIG options must not use lower-case letter. Convert this and related
ones to upper case.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@foundries.io>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 89c2986..9542303 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1361,7 +1361,7 @@
 
 dtb-$(CONFIG_ARCH_STI) += stih410-b2260.dtb
 
-dtb-$(CONFIG_STM32MP13x) += \
+dtb-$(CONFIG_STM32MP13X) += \
 	stm32mp135f-dk.dtb
 
 dtb-$(CONFIG_STM32MP15x) += \