drivers: target: Mark function as static in target_core_iblock.c

Mark function iblock_get_write_cache() as static in target_core_iblock.c
because it is not used outside this file.

This eliminates the following warning in target_core_iblock.c:
drivers/target/target_core_iblock.c:766:6: warning: no previous prototype for ‘iblock_get_write_cache’ [-Wmissing-prototypes]
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_iblock.c

@@ -763,7 +763,7 @@ iblock_parse_cdb(struct se_cmd *cmd)
 	return sbc_parse_cdb(cmd, &iblock_sbc_ops);
 }
 
-bool iblock_get_write_cache(struct se_device *dev)
+static bool iblock_get_write_cache(struct se_device *dev)
 {
 	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
 	struct block_device *bd = ib_dev->ibd_bd;