Input: sparse-keymap - switch to using new keycode interface

Switch sparse keymap library to use new style of getkeycode and
setkeycode methods to allow retrieving and setting keycodes not
only by their scancodes but also by index.

Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>