stm32mp1: split clkfunc code

Create a new file stm32mp_clkfunc.c to put functions that could be common
between several platforms.

Change-Id: Ica915c796b162b2345056b33328acc05035a242c
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/drivers/st/clk/stm32mp1_clk.c b/drivers/st/clk/stm32mp1_clk.c
index 2e89ecf..4275f3b 100644
--- a/drivers/st/clk/stm32mp1_clk.c
+++ b/drivers/st/clk/stm32mp1_clk.c
@@ -18,10 +18,10 @@
 #include <common/debug.h>
 #include <drivers/delay_timer.h>
 #include <drivers/generic_delay_timer.h>
+#include <drivers/st/stm32mp_clkfunc.h>
 #include <drivers/st/stm32mp1_clk.h>
 #include <drivers/st/stm32mp1_clkfunc.h>
 #include <drivers/st/stm32mp1_rcc.h>
-#include <dt-bindings/clock/stm32mp1-clks.h>
 #include <dt-bindings/clock/stm32mp1-clksrc.h>
 #include <lib/mmio.h>
 #include <lib/utils_def.h>