greybus: camera: Set link power mode to HS-G2 with 2 lanes

HS-G1 isn't enough for all camera modules. The gear will need to be
computed dynamically, but for now hardcode it to 2 with 2 lanes.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>