Input: samsung-keypad - use of_match_ptr()

Instead of having to define the match table to NULL if CONFIG_OF isn't
set, use the of_match_ptr() macro which will do this for us.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>