Input: ep93xx_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/20220923194738.927408-5-dmitry.torokhov@gmail.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>