Input: sh_keysc - 8x8 MODE_6 fix

According to the data sheet for G4, AP4 and AG5 KEYSC MODE_6 is 8x8 keys.
Bump up MAXKEYS to 64 too.

Signed-off-by: Magnus Damm <damm@opensource.se>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>