dt-bindings: watchdog: add stm32mp1 support

This patch adds support of stm32mp1.
stm32mp1 requires 2 clocks lsi and pclk.
Signed-off-by: NLudovic Barre <ludovic.barre@st.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck Linux@roeck-us.net>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/st,stm32-iwdg.txt

@@ -2,9 +2,15 @@ STM32 Independent WatchDoG (IWDG)
 ---------------------------------
 
 Required properties:
-- compatible: "st,stm32-iwdg"
-- reg: physical base address and length of the registers set for the device
-- clocks: must contain a single entry describing the clock input
+- compatible: Should be either:
+  - "st,stm32-iwdg"
+  - "st,stm32mp1-iwdg"
+- reg: Physical base address and length of the registers set for the device
+- clocks: Reference to the clock entry lsi. Additional pclk clock entry
+  is required only for st,stm32mp1-iwdg.
+- clock-names: Name of the clocks used.
+  "lsi" for st,stm32-iwdg
+  "lsi", "pclk" for st,stm32mp1-iwdg
 
 Optional Properties:
 - timeout-sec: Watchdog timeout value in seconds.
@@ -15,5 +21,6 @@ iwdg: watchdog@40003000 {
 	compatible = "st,stm32-iwdg";
 	reg = <0x40003000 0x400>;
 	clocks = <&clk_lsi>;
+	clock-names = "lsi";
 	timeout-sec = <32>;
 };