ARM: 7513/1: Make sure dtc is built before running it

'make dtbs' in a clean tree will try running the dtc before actually
building it.  Make these rules depend upon the scripts to build it.

Cc: <stable@vger.kernel.org>
Signed-off-by: NDavid Brown <davidb@codeaurora.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Makefile

@@ -284,10 +284,10 @@ zImage Image xipImage bootpImage uImage: vmlinux
 zinstall uinstall install: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@
 
-%.dtb:
+%.dtb: scripts
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
 
-dtbs:
+dtbs: scripts
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
 
 # We use MRPROPER_FILES and CLEAN_FILES now