at76c50x-usb: additional disconnect fixes
at76c50x-usb: additional disconnect fixes

Additional attempts to fix Oops on disconnect, that appear to be successful.
However, some may be extraneous.

The cancel_delayed_work call is probably the most necessary.  The
device_unplugged check may not be necessary.  del_timer_sync may not
be necessary either, but the Oops I was receiving was related to
timers.  Hence the addition.

Signed-off-by: Jason Andryuk <8558cf2f125c210e58f86c566cb85d5e97963455@gmail.com>
Signed-off-by: Kalle Valo <caa20ba0e0e4cb20683f1eb6eacae433f722076d@iki.fi>
Signed-off-by: John W. Linville <2a53bac7a5d324865ef46ec4c38b2c0fba1456b4@tuxdriver.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas