dm: arm: imx: cx9020: enable DM_GPIO

Switch to DM_GPIO and add gpio_request where necessary.
This is needed for DM_VIDEO and fixes an issue with sd card detection
which was introduced by the combination of these commits:

commit 7a0425dd ("mmc: fsl_esdhc: make get_cd work well in dm_mmc_ops")
commit 7e04b4c7 ("dm: arm: imx: migrate cx9020 to CONFIG_DM_MMC")

Acked-by: Patrick Bruenn <p.bruenn@beckhoff.com>
Signed-off-by: Steffen Dirkwinkel <s.dirkwinkel@beckhoff.com>