ARM: 6244/1: mmci: add variant data and default MCICLOCK support

Add a variant_data structure to handle the differences between the
various variants of this peripheral.  Add a first quirk for a default
MCICLOCK value, required on the Ux500 variant where the enable bit needs
to be always set, since it controls access to some registers.

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>