This avoids problems when building on SPARC targets due to the driver
calling the bus abstraction layer 'sbus'.  Not that any SBUS-sporting
SPARC targets are likely to have an SDIO controller, but this is the
correct thing to do.

See http://kisskb.ellerman.id.au/kisskb/buildresult/8846508/Signed-off-by: Solomon Peachy <pizza@shaftnet.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>