ARM: 6309/1: mmci: allow neither ->status nor gpio_cd to be specified

The card may be always present on the board, and for these cases neither
a status callback nor a card detect GPIO is required, and card detection
polling can be disabled.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>