Autostart Motion when OpenWRT boots

Make sure the config file is set to daemon mode - this lets openwrt run in the background
Open /etc/motion.conf using WinSCP and make sure daemon is set to on...

daemon on

save and close

Then load on boot.....

Open /etc/rc.local using WinSCP and replace with the following....

# Put your custom commands here that should be executed once
# the system init finished. By default this file does nothing.
motion -c /etc/motion.conf
exit 0

Save and reboot, then it will then load automatically on startup.

Edit.......
I had an intermittent problem on reboot
In the kernel log on reboot I was getting:-
UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround.
It worked if I unplugged the camera and plugged it back in, or I power cycled the router just not on reboot (using reset button or from reboot in luci).
To get it working reliably on reboot, I had to edit /etc/modules.d/video-uvc to read

uvcvideo quirks=0x100


save and reboot