ARM: 6530/1: mmci: partially revert clock divisor code

I misread the datasheet as if bypass mode was not available at all
on the ux500's, I was wrong. It is there, the datasheet just
states that you should not have to use it.

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