As hinted in the linux kernel driver, pxa platforms such as mainstone,
stargate and idp have a broken design, where half-word writes not
aligned to a word address are not working.

This patch is a taking back the half-word write accessor for this
specific case from the linux kernel.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>