soc: microchip: sam: set CONFIG_MFD to 'y' when FLEXCOM is used

When there are FLEXCOM nodes in the device tree, set CONFIG_MFD to
'y' automatically.

Signed-off-by: Tony Han <tony.han@microchip.com>

Author: TonyHan11

soc/microchip/sam/Kconfig.defconfig

@@ -10,4 +10,8 @@ rsource "*/Kconfig.defconfig"
 config CLOCK_CONTROL
 	default y
 
+config MFD
+	default y
+	depends on DT_HAS_MICROCHIP_SAM_FLEXCOM_ENABLED
+
 endif # SOC_FAMILY_MICROCHIP_SAM