[MMC] Fix chip config in wbsd

There is a broken if clause in the wbsd driver that can cause the
driver to try and configure the chip even though none is found. This
results in i/o on invalid ports.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>