scsi: ufs-bsg: Change the calling convention for write descriptor

When we had a write descriptor query upiu, we appended the descriptor right
after the bsg request.  This was fine as the bsg driver allows to allocate
whatever buffer we needed in its job request.

Still, the proper way to deliver payload, however small (we only write
config descriptors of 144 bytes), is by using the job request payload data
buffer.

So change this ABI now, while ufs-bsg is still new, and nobody is actually
using it.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Evan Green <evgreen@chromium.org>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>