target: need_to_release is always false, remove redundant check and kfree

The removal the #ifdef'd code on CONFIG_ARCH_HAS_SG_CHAIN in
commit 02c4de53 ("target/rd: always chain S/G list")
removed the setting of need_to_release to true, so we are now left
with need_to_release always being false and hence the conditional
kfree is never reached.  Clean up the dead code by removing need_to_release
and the conditional kfree.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_rd.c

@@ -403,7 +403,6 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, bool is_read)
 	struct se_device *se_dev = cmd->se_dev;
 	struct rd_dev *dev = RD_DEV(se_dev);
 	struct rd_dev_sg_table *prot_table;
-	bool need_to_release = false;
 	struct scatterlist *prot_sg;
 	u32 sectors = cmd->data_length / se_dev->dev_attrib.block_size;
 	u32 prot_offset, prot_page;
@@ -432,9 +431,6 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, bool is_read)
 	if (!rc)
 		sbc_dif_copy_prot(cmd, sectors, is_read, prot_sg, prot_offset);
 
-	if (need_to_release)
-		kfree(prot_sg);
-
 	return rc;
 }