i40evf: propagate interrupt allocation failure

Lower level functions are properly reporting errors, and higher-level
functions are correctly responding to errors, but the errors aren't
actually getting through. Typically, the middle-manager function seems
to want to shield its boss from any bad news.

This change fixes a panic if the driver is unable to enable MSI-X or is
unable to acquire enough vectors.

Change-ID: Ifd5787ce92519a5d97e4b465902db930d97b71a1
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>