Staging: dt3155: remove the driver

There is now a proper V4L driver for this device in the tree,
so remove this one.

Cc: Scott Smedley <ss@aao.gov.au>
Cc: H Hartley Sweeten <hartleys@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>