imx8m: ddrphy_utils: Improve coding style

Currently checkpatch is not happy about this file:

total: 14 errors, 2 warnings, 7 checks, 359 lines checked

Improve the coding style so that it can now report:

total: 0 errors, 0 warnings, 6 checks, 360 lines checked

Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>