more command usage cleanup

Fix up a few dangling commands like in "Command usage cleanup" commit.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/cmd_mmc.c b/common/cmd_mmc.c
index 16c919b..ee94470 100644
--- a/common/cmd_mmc.c
+++ b/common/cmd_mmc.c
@@ -166,7 +166,7 @@
 
 U_BOOT_CMD(
 	mmc, 6, 1, do_mmcops,
-	"mmc	- MMC sub system\n",
+	"MMC sub system",
 	"mmc read <device num> addr blk# cnt\n"
 	"mmc write <device num> addr blk# cnt\n"
 	"mmc rescan <device num>\n"