ARM: dtb: move all dtb targets to common Makefile

Since the dtb targets have moved to arch/arm/boot/dts/Makefile, sweep
the platforms that have had new targets added recently and move them over.

While I was at it, I also made the dtb generation more generic, i.e. if
the platform is enabled then all dtbs for that platform will be created.

Signed-off-by: Olof Johansson <olof@lixom.net>
Cc: Tony Lindgren <tony@atomide.com>
Cc: David Brown <davidb@codeaurora.com>
Cc: Barry Song <Baohua.Song@csr.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Stephen Warren <swarren@wwwdotorg.org>

arch/arm/mach-omap2/Makefile.boot

@@ -1,9 +1,3 @@
   zreladdr-y		+= 0x80008000
 params_phys-y		:= 0x80000100
 initrd_phys-y		:= 0x80800000
-
-dtb-$(CONFIG_SOC_OMAP2420)	+= omap2420-h4.dtb
-dtb-$(CONFIG_ARCH_OMAP3)	+= omap3-beagle-xm.dtb omap3-evm.dtb omap3-tobi.dtb
-dtb-$(CONFIG_ARCH_OMAP4)	+= omap4-panda.dtb omap4-pandaES.dtb
-dtb-$(CONFIG_ARCH_OMAP4)	+= omap4-var_som.dtb omap4-sdp.dtb
-dtb-$(CONFIG_SOC_OMAP5)		+= omap5-evm.dtb