soc: imx: Add i.MX8MP SoC driver support

Add i.MX8MP SoC driver support:

root@imx8mpevk:~# cat /sys/devices/soc0/family
Freescale i.MX

root@imx8mpevk:~# cat /sys/devices/soc0/machine
FSL i.MX8MP EVK

root@imx8mpevk:~# cat /sys/devices/soc0/soc_id
i.MX8MP

root@imx8mpevk:~# cat /sys/devices/soc0/revision
1.0

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>