arm: fix i2c-pxa build

From commit 7d054817:
> According to the PXA27x developer's manual, we shall do so.

We shall also at least compile test our changes.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>