ARM: imx: ddr: Fill in missing DDRC ZQCTLx on i.MX7

The iMX7 defines further DDRC ZQCTLx registers, however those were
thus far missing from the list of registers and not programmed. On
systems with LPDDR2 or DDR3, those registers must be programmed with
correct values, otherwise the DRAM may not work. However, existing
systems which worked without programming these registers before are
now setting those registers to 0, which is the default value, so no
functional change there.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>