USB: garmin_gps: fix memory leak on disconnect

commit 618aa1068df29c37a58045fe940f9106664153fd upstream.

Remove bogus disconnect test introduced by 95bef012e ("USB: more serial
drivers writing after disconnect") which prevented queued data from
being freed on disconnect.

The possible IO it was supposed to prevent is long gone.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>