mmc: mvsdio: Remove redundant use of mmc_gpio_free_cd|ro()

The MMC core makes use of the devm_* functions while requesting the
CD/WP GPIOs, let's rely on that.

Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>