ARM: s3c64xx: include header defining input event codes

ARM: s3c64xx: include header defining input event codes

The board file for Wolfson Cragganmore 6410 uses various KEY_* defines,
but does not include the relevant header directly and instead relies on
other headers to include it indirectly. With the upcoming cleanup of
matrix_keypad.h this indirection is now broken and we should include the
relevant header directly.

Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/Y1wHwEm15/K87tdq@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>