This adds the DDR driver for the i.MX8MQ/i.MX8MM. It's taken from
U-Boot v2020.04-rc1 with slight modifications for barebox

The i.MX8MQ boards in the tree currently use the output of an earlier
version of the NXP i.MX8M DDR Tool which doesn't use a controller driver
but instead does most stuff in board code. It seems this can coexist
with the new driver, only a few helper functions that previously lived
in arch/arm/mach-imx/imx8-ddrc.c are now provided by the new driver.

Tested on an i.MX8MM EVK

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The phyCORE-i.MX8M aka PCL-066 is a SoM containing a i.MX8M SoC.

phyCORE-i.MX8M:
 - 1GB LPDDR4 RAM
 - eMMC
 - microSD
 - Ethernet

Signed-off-by: Christian Hemp <christian.hemp@posteo.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>