Staging: dt3155: make module_{init/exit} functions static

The module_init() and module_exit() functions should be static and marked
with __init and __exit.

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