virtchnl: i40e/iavf: rename iwarp to rdma

Since the latest Intel hardware does both IWARP and ROCE, rename the
term IWARP in the virtchnl header to be RDMA. Do this for both upper and
lower case instances. Many of the non-virtchnl.h changes were done with
regular expression replacements using perl like:
perl -p -i -e 's/_IWARP/_RDMA/' <files>
perl -p -i -e 's/_iwarp/_rdma/' <files>
and I had to pick up a few instances manually.

The virtchnl.h header has some comments and clarity added around when to
use certain defines.

note: had to fix a checkpatch warning for a long line by wrapping one of
the lines I changed.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Jakub Andrysiak <jakub.andrysiak@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>