mmc: fsl_esdhc: make GPIO support optional

mmc: fsl_esdhc: make GPIO support optional

There would be compiling error as below when enable driver model for esdhc.
undefined reference to `dm_gpio_get_value'
undefined reference to `gpio_request_by_name_nodev'
This patch is to make GPIO support optional with CONFIG_DM_GPIO. Because
all boards of QorIQ platform don't need it and they just check register for
CD/WP status, only some boards of i.MX platform require this.

Signed-off-by: Yangbo Lu <[email protected]>
Acked-by: Jaehoon Chung <[email protected]>
Reviewed-by: York Sun <[email protected]>