plat: imx: Add i.MX8MQ basic support

i.MX8MQ is new SOC of NXP's i.MX8M family based on
A53. It can provide industry-leading audio, voice
and video processing for applications that scale
from consumer home audio to industrial building
automation and mobile computers

this patchset add the basic supoort to boot up
the 4 X A53. more feature will be added later.

Signed-off-by: Bai Ping <ping.bai@nxp.com>