drivers: disk: sdmmc_stm32 support for clock divisor

Adds support for a devicetree property that controls the ClockDiv
value provided to the SDIO during init.

Signed-off-by: Maxmillion McLaughlin <github@maxmclau.com>

drivers/disk/sdmmc_stm32.c

@@ -689,6 +689,9 @@ static struct stm32_sdmmc_priv stm32_sdmmc_priv_1 = {
 	.hsd = {
 		.Instance = (MMC_TypeDef *)DT_INST_REG_ADDR(0),
 		.Init.BusWide = SDMMC_BUS_WIDTH,
+#if DT_INST_NODE_HAS_PROP(0, clk_div)
+		.Init.ClockDiv = DT_INST_PROP(0, clk_div),
+#endif
 	},
 #if DT_INST_NODE_HAS_PROP(0, cd_gpios)
 	.cd = GPIO_DT_SPEC_INST_GET(0, cd_gpios),

dts/bindings/mmc/st,stm32-sdmmc.yaml

@@ -39,6 +39,13 @@ properties:
       - 4
       - 8
 
+  clk-div:
+    type: int
+    default: 0
+    description: |
+        Clock division factor for SDMMC. Typically the clock operates at 25MHz so
+        a division factor of 2 would be 25MHz / 2 = 12.5MHz.
+
   idma:
     type: boolean
     description: |