ARM: 6894/1: mmci: trigger card detect IRQs on falling and rising edges

Right now the card detect IRQ for MMCI is requested without any
flags which will give some default machine-specified IRQ
behaviour. However on the U300 rising+falling edges (such as can
be expected from a simple GPIO to generate when inserting/removing
a card) need to be requested explicitly.

Cc: Rabin Vincent <rabin.vincent@stericsson.com>
Cc: Ulf Hansson <ulf.hansson@stericsson.com>
Cc: Sebastian Rasmussen <sebastian.rasmussen@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>