USB: Remove EXPERIMENTAL designation from USB MDC800 support.

Since support for the USB Mustek MDC800 Digital Camera has apparently
been around since the beginning of the git repository, it's safe to
assume it's no longer experimental.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>