ARM: 6245/1: mmci: enable hardware flow control on Ux500 variants

Although both the U300 and Ux500 use ST variants, the HWFCEN bits are at
different positions, so use the variant_data to store the information.

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>