board: engicam: Attach i.MX6 common code

The existing common code for Engicam boards uses i.MX6,
so attach that into i.MX6 Engicam boards so-that adding
new SoC variants of Engicam boards become meaningful.

Add support for it.

Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever <Yang&lt;kever.yang@rock-chips.com>