counter: stm32-timer-cnt: remove iio headers

The stm32-timer-cnt driver doesn't use the iio interface. The iio headers
aren't relevant and can be removed as reported by William in [1].
With this change, mod_devicetable.h needs to be added to define the
'of_device_id' struct.

[1] https://lkml.org/lkml/2020/2/10/1516Reported-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/counter/stm32-timer-cnt.c

@@ -8,9 +8,8 @@
  *
  */
 #include <linux/counter.h>
-#include <linux/iio/iio.h>
-#include <linux/iio/types.h>
 #include <linux/mfd/stm32-timers.h>
+#include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>