staging: vt6656: clean-up registers initialization error path

Avoid discarding function's return code during register initialization.
Handle it instead and return 0 on success or a negative errno value on
error.

Signed-off-by: Quentin Deslandes <quentin.deslandes@itdev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>