ARM: 5896/1: MMCI: work around a hardware bug in U300

In the U300 some hardware bug makes the status flag not come up
signalling a successful write (or anything else, like an error, for
that matter) on write requests. This little quirk makes the writes
work on U300.

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