i40evf: don't wait so long

We really don't need to delay an entire millisecond just to get into our
critical section. A microsecond will be sufficient, thank you.

Change-ID: I2d02ece6610007d98cabcb3f42df9a774bb54e59
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>