[SCSI] target: Minor sparse warning fixes and annotations

This patch addresses the majority of sparse warnings and adds
proper locking annotations.  It also fixes the dubious one-bit signed
bitfield, for which the signed one-bit types can be 0 or -1 which can
cause a problem if someone ever checks if (foo->lu_gp_assoc == 1).
The current code is fine because everyone just checks zero vs non-zero.
But Sparse complains about it so lets change it.  The warnings look like
this:

include/target/target_core_base.h:228:26: error: dubious one-bit signed bitfield

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Fubo Chen <fubo.chen@gmail.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ff9ace0..80df405 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -227,8 +227,6 @@
 static int transport_set_sense_codes(struct se_cmd *cmd, u8 asc, u8 ascq);
 static void transport_stop_all_task_timers(struct se_cmd *cmd);
 
-int transport_emulate_control_cdb(struct se_task *task);
-
 int init_se_global(void)
 {
 	struct se_global *global;
@@ -4395,7 +4393,7 @@
 	return -1;
 }
 
-extern u32 transport_calc_sg_num(
+u32 transport_calc_sg_num(
 	struct se_task *task,
 	struct se_mem *in_se_mem,
 	u32 task_offset)