boards: nucleo_l432kc: Use dts for clocks configuration

Convert board to use of device tree for clocks configuration.

Signed-off-by: Alexandre Bourdiol <alexandre.bourdiol@st.com>
diff --git a/boards/arm/nucleo_l432kc/nucleo_l432kc.dts b/boards/arm/nucleo_l432kc/nucleo_l432kc.dts
index 2602c3e..4219402 100644
--- a/boards/arm/nucleo_l432kc/nucleo_l432kc.dts
+++ b/boards/arm/nucleo_l432kc/nucleo_l432kc.dts
@@ -33,6 +33,28 @@
 	};
 };
 
+&clk_hsi {
+	status = "okay";
+};
+
+&pll {
+	div-m = <1>;
+	mul-n = <20>;
+	div-p = <7>;
+	div-q = <2>;
+	div-r = <4>;
+	clocks = <&clk_hsi>;
+	status = "okay";
+};
+
+&rcc {
+	clocks = <&pll>;
+	clock-frequency = <DT_FREQ_M(80)>;
+	ahb-prescaler = <1>;
+	apb1-prescaler = <1>;
+	apb2-prescaler = <1>;
+};
+
 &usart1 {
 	pinctrl-0 = <&usart1_tx_pa9 &usart1_rx_pa10>;
 	current-speed = <115200>;