ixgbe: cleanup short msleep's (<20ms) to use usleep_range

Since msleep might not sleep for the desired amount when less
than 20ms use usleep_range.

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>