commands: fix a warning in help.c

Fix the following warning:

commands/help.c: In function ‘list_group’:
commands/help.c:57:4: warning: format not a string literal and
no format arguments [-Wformat-security]
    printf(cmdtp->name);
    ^

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands/help.c

@@ -54,7 +54,7 @@ static void list_group(int verbose, const char *grpname, uint32_t group)
 				printf(", ");
 				pos += 2;
 			}
-			printf(cmdtp->name);
+			puts(cmdtp->name);
 			pos += len;
 		}
 	}