ARM: imx: Revert "dh_imx6: Switch to full DM-aware"

ARM: imx: Revert "dh_imx6: Switch to full DM-aware"

This reverts commit 03a673cf49e ("dh_imx6: Switch to full DM-aware").
According to discussion [1], the patch is known to break the dh_imx6
board, however it made it upstream just before 2021.01-rc4, likely by
mistake. Revert this patch to put the board back into working order.

Also note that this board has no DM SPL support due to OCRAM size
limitations, but that is fine, as SPL DM support is optional.

[1] https://lists.denx.de/pipermail/u-boot/2020-June/417986.html

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andreas Geisreiter <ageisreiter@dh-electronics.de>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Ludwig Zenz <lzenz@dh-electronics.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tom Rini <trini@konsulko.com>