ixgbevf: add wait for Rx queue disable

New function was added to wait for Rx queues to be disabled before
disabling NAPI. This function also allows us to  modify
ixgbevf_rx_desc_queue_enable() to better match ixgbe.  I also cleaned up
some msleep calls to usleep_range while I was in this code anyway.

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>