mmc: tmio: move mmc_gpio_request_cd() before mmc_add_host()

Drivers do not need to call mmc_gpiod_request_cd_irq() explicitly
because mmc_start_host() calls it.  To make it work, cd_gpio must
be set before mmc_add_host().

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>