IB/srpt: Fix ACL lookup during login

Make sure that the initiator port GUID is stored in ch->ini_guid.
Note: when initiating a connection sgid and dgid members in struct
sa_path_rec represent the source and destination GIDs. When accepting
a connection however sgid represents the destination GID and dgid the
source GID.

Fixes: commit 2bce1a6d ("IB/srpt: Accept GUIDs as port names")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>