i40e: Add common function for finding VSI by type

This patch adds a common method for finding a VSI by type.  The main
motivation for doing this is that the Flow Director path actually had two
ways of handling this, one stopped on first match and one did not.  This
patch makes it so that all callers of this function will get the same
approach for finding a VSI.

Change-ID: Ibf25de8acd8466582520694424aa87da66965fbd
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Bimmy Pujari <bimmy.pujari@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>