Command usage cleanup

Remove command name from all command "usage" fields and update
common/command.c to display "name - usage" instead of
just "usage". Also remove newlines from command usage fields.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_mmc.c b/common/cmd_mmc.c
index 25c9702..473825e 100644
--- a/common/cmd_mmc.c
+++ b/common/cmd_mmc.c
@@ -36,6 +36,6 @@
 
 U_BOOT_CMD(
 	mmcinit,	1,	0,	do_mmc,
-	"mmcinit - init mmc card\n",
+	"init mmc card",
 	NULL
 );