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_diag.c b/common/cmd_diag.c
index 13d4225..c2a6175 100644
--- a/common/cmd_diag.c
+++ b/common/cmd_diag.c
@@ -66,7 +66,7 @@
 
 U_BOOT_CMD(
 	diag,	CONFIG_SYS_MAXARGS,	0,	do_diag,
-	"diag    - perform board diagnostics\n",
+	"perform board diagnostics",
 	     "    - print list of available tests\n"
 	"diag [test1 [test2]]\n"
 	"         - print information about specified tests\n"