target: Fix compile warning w/ missing module.h include

This patch fixes the following compile warning in target_core_cdb.c in
recent linux-next code due to the new use of EXPORT_SYMBOL() for
target_get_task_cdb().

drivers/target/target_core_cdb.c:1316: warning: data definition has no type or storage class
drivers/target/target_core_cdb.c:1316: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
drivers/target/target_core_cdb.c:1316: warning: parameter names (without types) in function declaration
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_cdb.c

@@ -24,6 +24,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <asm/unaligned.h>
 #include <scsi/scsi.h>