arm: Rename STM32MP15x

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: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/board/st/common/Kconfig b/board/st/common/Kconfig
index 6d1b76b..5efac65 100644
--- a/board/st/common/Kconfig
+++ b/board/st/common/Kconfig
@@ -1,7 +1,7 @@
 config CMD_STBOARD
 	bool "stboard - command for OTP board information"
 	depends on ARCH_STM32MP
-	default y if TARGET_ST_STM32MP25X || TARGET_ST_STM32MP15x || TARGET_ST_STM32MP13X
+	default y if TARGET_ST_STM32MP25X || TARGET_ST_STM32MP15X || TARGET_ST_STM32MP13X
 	help
 	  This compile the stboard command to
 	  read and write the board in the OTP.