staging: vt6655: Remove vif check from vnt_interrupt

staging: vt6655: Remove vif check from vnt_interrupt

BugLink: https://bugs.launchpad.net/bugs/1838116
commit cc26358f89c3e493b54766b1ca56cfc6b14db78a upstream.

A check for vif is made in vnt_interrupt_work.

There is a small chance of leaving interrupt disabled while vif
is NULL and the work hasn't been scheduled.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
CC: stable@vger.kernel.org # v4.2+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>