ixgbevf: Adds function to set PSRTYPE register

This patch creates a new function to set PSRTYPE. This function helps lay
the ground work for eventual multi queue support.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>