[MMC] Fix base address configuration in wbsd

There were some confusion about base I/O variables in the wbsd driver.
Seems like things have been working on shear luck so far. The global 'io'
variable (used when manually configuring the resources) was used instead of
the local 'base' variable.

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