mdadm:add 'clustered' in typo prompt when specify wrong param for bitmap

mdadm: 'clustered' bitmap has already supported, thus add the
         prompt if users specify wrong value for bitmap param.

Signed-off-by: Zhilong Liu <zlliu@suse.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>

mdadm.c

@@ -1142,7 +1142,7 @@ int main(int argc, char *argv[])
 				continue;
 			}
 			/* probable typo */
-			pr_err("bitmap file must contain a '/', or be 'internal', or 'none'\n"
+			pr_err("bitmap file must contain a '/', or be 'internal', or be 'clustered', or 'none'\n"
 				"       not '%s'\n", optarg);
 			exit(2);