boards: stm32f412g_disco: Use dts for clocks configuration

Convert board to use of device tree for clocks configuration.

Signed-off-by: Alexandre Bourdiol <alexandre.bourdiol@st.com>

boards/arm/stm32f412g_disco/stm32f412g_disco.dts

@@ -72,6 +72,29 @@
 	};
 };
 
+&clk_hse {
+	hse-bypass;
+	clock-frequency = <DT_FREQ_M(8)>; /* STLink 8MHz clock */
+	status = "okay";
+};
+
+&pll {
+	div-m = <4>;
+	mul-n = <100>;
+	div-p = <2>;
+	div-q = <8>;
+	clocks = <&clk_hse>;
+	status = "okay";
+};
+
+&rcc {
+	clocks = <&pll>;
+	clock-frequency = <DT_FREQ_M(100)>;
+	ahb-prescaler = <1>;
+	apb1-prescaler = <2>;
+	apb2-prescaler = <1>;
+};
+
 &usart2 {
 	pinctrl-0 = <&usart2_tx_pa2 &usart2_rx_pa3>;
 	current-speed = <115200>;

boards/arm/stm32f412g_disco/stm32f412g_disco_defconfig

@@ -2,8 +2,6 @@
 
 CONFIG_SOC_SERIES_STM32F4X=y
 CONFIG_SOC_STM32F412ZG=y
-# 100MHz system clock (highest value to get a precise USB clock should be 96MHz)
-CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=100000000
 
 # Enable MPU
 CONFIG_ARM_MPU=y
@@ -23,22 +21,5 @@ CONFIG_PINMUX=y
 # enable GPIO ports A, B, C, D, E
 CONFIG_GPIO=y
 
-# clock configuration
+# Enable Clocks
 CONFIG_CLOCK_CONTROL=y
-
-# Clock configuration for Cube Clock control driver
-CONFIG_CLOCK_STM32_HSE_CLOCK=8000000
-CONFIG_CLOCK_STM32_SYSCLK_SRC_PLL=y
-# use HSE as PLL input
-CONFIG_CLOCK_STM32_PLL_SRC_HSE=y
-# however, the board does not have an external oscillator, so just use
-# the 8MHz clock signal coming from integrated STLink
-CONFIG_CLOCK_STM32_HSE_BYPASS=y
-# produce 100MHz clock at PLL output
-CONFIG_CLOCK_STM32_PLL_M_DIVISOR=4
-CONFIG_CLOCK_STM32_PLL_N_MULTIPLIER=100
-CONFIG_CLOCK_STM32_PLL_P_DIVISOR=2
-CONFIG_CLOCK_STM32_PLL_Q_DIVISOR=8
-CONFIG_CLOCK_STM32_AHB_PRESCALER=1
-CONFIG_CLOCK_STM32_APB1_PRESCALER=2
-CONFIG_CLOCK_STM32_APB2_PRESCALER=1