[SCSI] fcoe: fix regression on offload em matching function for initiator/target

[SCSI] fcoe: fix regression on offload em matching function for initiator/target

This is a regression introduced by commit
1ff9918b625457ce20d450d00f9ed0a12ba191b7 The else statement here is breaking
the initiator logic of allocating xid from the offloaded em xid pool for READ
I/O only to use DDP, as shown by the snippet of trace below, where the WRITE
is using xid 0x5 from the offloaded em xid pool:

Protocol VID Len S_ID        D_ID     OX_ID  RX_ID  Summary
..
*FCP     228 96  0b.08.01 -> 01.0f.00 0x0005 0xffff SCSI: Write(10) LUN: 0x00
 FCP     228 76  01.0f.00 -> 0b.08.01 0x0005 0x828d XFER_RDY
...

The bug is in the else statement, for both initiator and target, the
new command will have FC frame header bit 23 (FC_FC_EX_CTX) cleared as it was
originated from the initiator. Also, this is assuming the frame header is
already filled up, which is only true for target since for initiator, this is a
new frame and oem_match gets called when em tries get xid for this i/o before
it is filled up and sent out.

The fix is to check if there is a fc_fcp_pkt associated w/ this frame from
fr_fsp(fp), since fr_fsp(fp) is NULL for tcm_fc target and non-I/O frame in
initiator. This should also return true for target only if it is an
FC_RCTL_DD_UNSOL_CMD and rx_id is not allocated.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>