mmc: remove .owner field for drivers using module_platform_driver

This patch removes the superflous .owner field for drivers which
use the module_platform_driver API, as this is overriden in
platform_driver_register anyway.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>