new default shortcut to config & build a board

The majority of the time that I build things in U-Boot, I want to just
build for the board.  I don't make board config tweaks after selecting the
board.  So add a new pattern rule that allows people to combine two steps
in one go:
	`make foo_config && make` => `make foo`

This shouldn't conflict with any existing make rules as the pattern rule
is used only the rule doesn't already exist.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>

Makefile

@@ -501,6 +501,9 @@ unconfig:
 		$(obj)board/*/config.tmp $(obj)board/*/*/config.tmp \
 		$(obj)include/autoconf.mk $(obj)include/autoconf.mk.dep
 
+%: %_config
+	$(MAKE)
+
 #========================================================================
 # PowerPC
 #========================================================================
@@ -3542,10 +3545,6 @@ BFIN_BOARDS += ibf-dsp561
 $(BFIN_BOARDS:%=%_config)	: unconfig
 	@$(MKCONFIG) $(@:_config=) blackfin blackfin $(@:_config=)
 
-$(BFIN_BOARDS):
-	$(MAKE) $@_config
-	$(MAKE)
-
 #========================================================================
 # AVR32
 #========================================================================