adc: Drop dm.h header file

This header file should not be included in other header files. Remove it
and use a forward declaration instead.

Drop the common.h inclusion also.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/adc/stm32-adc-core.c

@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <asm/io.h>
 #include <dm/device_compat.h>
 #include <linux/bitops.h>

drivers/adc/stm32-adc-core.h

@@ -26,9 +26,9 @@
 #define STM32_ADC_MAX_ADCS		3
 #define STM32_ADCX_COMN_OFFSET		0x300
 
-#include <common.h>
 #include <clk.h>
-#include <dm.h>
+
+struct udevice;
 
 /**
  * struct stm32_adc_common - stm32 ADC driver common data (for all instances)

drivers/adc/stm32-adc.c

@@ -8,6 +8,7 @@
 
 #include <common.h>
 #include <adc.h>
+#include <dm.h>
 #include <asm/io.h>
 #include <dm/device_compat.h>
 #include <linux/bitops.h>