Input: nomadik-ske-keypad - add multi key press support

Added the multi key press support for SKE keypad by modifying the irq
function for handling the two different keys on the same column and also
pressing the two different keys of different columns on the same ASR
register.

Signed-off-by: Naveen Kumar Gaddipati <naveen.gaddipati@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>