imx: fix cpu_type helper

i.MX8MP use 0x182 as its ID, so 0xff is not valid to get the cpu type,
extend it to 0x1ff.

Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
1 file changed