MLK-16756 imx: imx8m: correct SOC type

MLK-16756 imx: imx8m: correct SOC type

Correct SoC type, otherwise get wrong soc type and access wrong
registers.
If not correct,  met kernel panic:
[    0.000000] Bad mode in Error handler detected on CPU0, code 0xbf000002 -- Sr
[    0.000000] Internal error: Oops - bad mode: 0 [#1] PREEMPT SMP
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.9.51-03585-gc9c62b70db7
[    0.000000] Hardware name: Freescale i.MX8MQ EVK (DT)
[    0.000000] task: ffff000009210700 task.stack: ffff000009200000
[    0.000000] PC is at setup_arch+0xf4/0x550
[    0.000000] LR is at setup_arch+0xf0/0x550
[    0.000000] pc : [<ffff0000090f2714>] lr : [<ffff0000090f2710>] pstate: 00005
[    0.000000] sp : ffff000009203f20
[    0.000000] x29: ffff000009203f20 x28: 00000000410f0018
[    0.000000] x27: 0000000000000400 x26: 00000000fff19b88
[    0.000000] x25: 00000000ff93a0b0 x24: 00000000fff83358
[    0.000000] x23: 0000000000000000 x22: ffff000009207000
[    0.000000] x21: ffff7dfffe800000 x20: ffff000009224000
[    0.000000] x19: ffff000008080000 x18: 0000000000000010
[    0.000000] x17: 0000000000009000 x16: 0000000000001800
[    0.000000] x15: 0000000000000006 x14: ffff00008933cbc7
[    0.000000] x13: ffff00000933cbd5 x12: 0000000000000000
[    0.000000] x11: 0000000000000007 x10: 0101010101010101
[    0.000000] x9 : ffffffffffffffff x8 : 0000000000000008
[    0.000000] x7 : 0000000000000007 x6 : 8000000000000000
[    0.000000] x5 : 0000000000000080 x4 : 000000000000006e
[    0.000000] x3 : 0000000000000000 x2 : 000000000000006e
[    0.000000] x1 : 0000000000000000 x0 : 0000000000000001

Signed-off-by: Peng Fan <peng.fan@nxp.com>