8139cp: re-enable interrupts after tx timeout

commit 01ffc0a7f1c1801a2354719dedbc32aff45b987d upstream.

Recovery doesn't work too well if we leave interrupts disabled...

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>