arm64: dts: move ns2 into northstar2 directory

Place northstar2 into its own subdirectory.  This helps as the number
of Broadcom boards grow and we can separate them per SoC.
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm64/boot/dts/broadcom/Makefile

 dtb-$(CONFIG_ARCH_BCM2835) += bcm2837-rpi-3-b.dtb
-dtb-$(CONFIG_ARCH_BCM_IPROC) += ns2-svk.dtb ns2-xmc.dtb
 
-dts-dirs	:= stingray
+dts-dirs	+= northstar2
+dts-dirs	+= stingray
 always		:= $(dtb-y)
 subdir-y	:= $(dts-dirs)
 clean-files	:= *.dtb

arch/arm64/boot/dts/broadcom/northstar2/Makefile

+dtb-$(CONFIG_ARCH_BCM_IPROC) += ns2-svk.dtb
+dtb-$(CONFIG_ARCH_BCM_IPROC) += ns2-xmc.dtb
+
+always		:= $(dtb-y)
+subdir-y	:= $(dts-dirs)
+clean-files	:= *.dtb