[SCSI] cxgb3i: add missing include

it needs scatterlist.h - indirect chain of includes doesn't work on a
lot of targets.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Karen Xie <kxie@chelsio.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>