iscsi: add libiscsi

There is a lot of code duplcited between iscsi_tcp and the upcoming iscsi_iser driver. This patch puts the duplicated code in a lib. There is more code to move around but this takes care of the
basics. For iscsi_offload if they use the lib we will probably move some things around. For example in the queuecommand we will not assume that the LLD wants to do queue_work, but it is better to handle that later when we know for sure what iscsi_offload looks like (we could probably do this for iscsi_iser though to).

Ideally I would like to get the iscsi_transports modules to a place where all they really have to do is put data on the wire, but how to do that will hopefully be more clear when we see other modules like iscsi_offload. Or maybe iscsi_offload will not use the lib and it will just be iscsi_iser and iscsi_tcp and maybe the iscsi_tcp_tgt if that is allowed in mainline.

index 81803a1..3ce80ab 100644
@@ -33,7 +33,7 @@ obj-$(CONFIG_SCSI_FC_ATTRS) 	+= scsi_tra
 obj-$(CONFIG_SCSI_ISCSI_ATTRS)	+= scsi_transport_iscsi.o
 obj-$(CONFIG_SCSI_SAS_ATTRS)	+= scsi_transport_sas.o
 
-obj-$(CONFIG_ISCSI_TCP) 	+= iscsi_tcp.o
+obj-$(CONFIG_ISCSI_TCP) 	+= libiscsi.o	iscsi_tcp.o
 obj-$(CONFIG_SCSI_AMIGA7XX)	+= amiga7xx.o	53c7xx.o
 obj-$(CONFIG_A3000_SCSI)	+= a3000.o	wd33c93.o
 obj-$(CONFIG_A2091_SCSI)	+= a2091.o	wd33c93.o

index b14ba7a..4fc623f 100644
@@ -148,7 +148,8 @@ enum iscsi_err {
 	ISCSI_ERR_SESSION_FAILED	= ISCSI_ERR_BASE + 13,
 	ISCSI_ERR_HDR_DGST		= ISCSI_ERR_BASE + 14,
 	ISCSI_ERR_DATA_DGST		= ISCSI_ERR_BASE + 15,
-	ISCSI_ERR_PARAM_NOT_FOUND	= ISCSI_ERR_BASE + 16
+	ISCSI_ERR_PARAM_NOT_FOUND	= ISCSI_ERR_BASE + 16,
+	ISCSI_ERR_NO_SCSI_CMD		= ISCSI_ERR_BASE + 17,
 };
 
 /*