ARM: spitz: include header defining input event codes

The board file for Sharp SL-Cxx00 Series of PDAs 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: Guenter Roeck <linux@roeck-us.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/Y/U+3PZsbLw++SnG@google.com


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