MAINTAINERS: update stm32mp1 path for arch

Handle correctly directory arch/arm/mach-stm32mp/ :
Add a trailing slash to include all files
and subdirectory files.
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>

MAINTAINERS

@@ -267,7 +267,7 @@ M:	Christophe Kerello <christophe.kerello@st.com>
 M:	Patrice Chotard <patrice.chotard@st.com>
 L:	uboot-stm32@st-md-mailman.stormreply.com (moderated for non-subscribers)
 S:	Maintained
-F:	arch/arm/mach-stm32mp
+F:	arch/arm/mach-stm32mp/
 F:	drivers/clk/clk_stm32mp1.c
 F:	drivers/i2c/stm32f7_i2c.c
 F:	drivers/misc/stm32mp_fuse.c