device-fsl

MA-15231 enable sysrq on imx8

At default, sysrq is disabled.
To enable it, add "androidboot.vendor.sysrq=1" in bootargs.

To trigger system reboot by sysrq, press below keys in minicom by order:
   <CTRL-a>, f, b
This can work even in user build mode.

Change-Id: Ifb41bb2428c6864359b5e3b2333f0e85d4feea37
Signed-off-by: Jindong <jindong.yue@nxp.com>
Reviewed-on: http://androidsource.ap.freescale.net/project/9583
Reviewed-by: zhang sanshan <sanshan.zhang@nxp.com>