[SCSI] fcoe: Unable to select the exchangeID from offload pool for storage targets

Problem: When initiator sends write command to target, target tries to
assign new sequence. It allocates new exchangeID (RX_ID)
always from non-offloaded pool (Non-offload EMA)

Fix: Enhanced fcoe_oem_match routine to look at F_CTL flags and if it
is exchange responder and command type is WRITEDATA, then function
returns TRUE instead of FALSE. This function is used to determine
which pool to use (offload pool of exchange is used only if this
function returns TRUE).

Technical Notes: N/A

Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>