rockchip: rk3399: Configure sdmmc regulator pinctrl in SPL

rockchip: rk3399: Configure sdmmc regulator pinctrl in SPL

A few boards have shown to be required to properly configure pinctrl
for the fixed regulator gpio pin used by sdmmc before being able to read
from SD-cards.

Include the related gpio, regulator and pinctrl nodes and enable related
Kconfig options so that pinctrl can be configured in SPL for boards that
may be affected by such issue.

Also change to imply SPL_DM_SEQ_ALIAS for all boards because it must be
enabled for working gpio usage in SPL after a future DT sync.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>