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/hush.c b/common/hush.c
index dbb4035..01b74d7 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -3625,7 +3625,7 @@
 
 U_BOOT_CMD(
 	showvar, CONFIG_SYS_MAXARGS, 1,	do_showvar,
-	"showvar- print local hushshell variables\n",
+	"print local hushshell variables",
 	"\n    - print values of all hushshell variables\n"
 	"showvar name ...\n"
 	"    - print value of hushshell variable 'name'\n"