ixgbevf: cleanup redundant mailbox read failure check

Since we are already checking for read failure in check_link we don't need
to do it here. Instead just make sure the watchdog task gets scheduled, if
we are up, and it can be done there. This will better follow igbvf method
of handling a mailbox event and message timeout.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>