Input: imx_keypad - add missing linux/input.h include

We are going to clean up matrix_keymap.h from unnecessary includes,
so the driver needs to include API that it uses directly.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220923194738.927408-4-dmitry.torokhov@gmail.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/imx_keypad.c

@@ -7,6 +7,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/input.h>
 #include <linux/input/matrix_keypad.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>