xprtrdma: Simplify rpcrdma_convert_kvec() and frwr_map()
Clean up.
Remove a conditional branch from the SGL set-up loop in frwr_map():
Instead of using either sg_set_page() or sg_set_buf(), initialize
the mr_page field properly when rpcrdma_convert_kvec() converts the
kvec to an SGL entry. frwr_map() can then invoke sg_set_page()
unconditionally.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Tom Talpey <tom@talpey.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>