Input: nomadik-ske-keypad - get rid of multiple interrupts

The keypad could cause multiple interrupts to be fired in succession
since we weren't waiting for the IRQs to clear properly in the
interrupt handler. We wait for a number of bus iterations (the
readl():s from the peripheral bus will stall, so these are quite
long) before giving up on getting keys ready to read, then we
sleep until the IRQ is deasserted (this is OK since the interrupt
is threaded). Also use the debounce platform data for another
hardcoded wait loop.

Signed-off-by: Naveen Kumar Gaddipati <naveen.gaddipati@stericsson.com>
Reviewed-by: Rikard Olsson <rikard.p.olsson@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>