clk: add driver for stm32mp1

add RCC clock driver for STMP32MP157
- base on driver model = UCLASS_CLK
- support ops to enable, disable and get rate
  of all SOC clock needed by U-Boot

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index e876c70..eb5ac6f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -199,6 +199,7 @@
 M:	Patrick Delaunay <patrick.delaunay@st.com>
 S:	Maintained
 F:	arch/arm/mach-stm32mp
+F:	clk/clk_stm32mp1.c
 F:	ram/stm32mp1
 
 ARM STM STV0991