Decouple SG support from HW ability to do UD checksum.
This coupling is for historical reasons and removed with 'commit
ec5f0615 ("net: Kill link between CSUM and SG features.")'

During driver load it is assumed that device does not supports SG. The
final decision is taken after creating UD QP based on device capability.
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>