compulab: imx8mm-cl-iot-gate: Fix some function declarations in ddr.h

We have a few places here that the function declarations do not
match their prototypes, correct them.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
Cc: Tom Rini <trini@konsulko.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reported-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>