i40evf: Do not clear MSI-X PBA manually

We should not be clearing the pending bit array for each vector manually.
The documentation for the hardware states that when in MSI-X mode the
pending bit array will be cleared automatically. Us clearing it ourselves
just results in multiple opportunities for us to drop an interrupt.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>