Makefile: let plain 'make' be like 'make all' again

That behaviour was broken by c96724af1baaa926cbcc8d8e5b19fd5ba339d962
(Makefile: add short help target). Also, update the helptext accordingly.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

Makefile

diff --git a/Makefile b/Makefile
index 240b748..0b7edbe 100644
--- a/Makefile
+++ b/Makefile
@@ -20,9 +20,11 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 #
 
+default: all
+
 help:
-	@echo "Common targets:"
-	@echo "  all		- build the standard set of utilities"
+	@echo "Common targets ('*' is default):"
+	@echo "* all		- build the standard set of utilities"
 	@echo "  debugtools	- build the debugging utilities"
 
 # Set this to 'false' if you do not need the socket-startup script