zynq: derive DEVICE_DTS from device definition name

In zynq target, the DEVICE_DTS variable is always set consistent
with the model part of the device definition name.

This patch replaces the redundant definitions for the individual
devices with a common recipe.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/zynq/image/Makefile

@@ -31,6 +31,7 @@ endef
 
 define Device/Default
 	PROFILES := Default
+	DEVICE_DTS := $(lastword $(subst _, ,$(1)))
 	KERNEL_DEPENDS = $$(wildcard $(DTS_DIR)/$$(DEVICE_DTS).dts)
 	KERNEL_INITRAMFS_PREFIX := $$(IMG_PREFIX)-$(1)-initramfs
 	KERNEL_PREFIX := $$(IMAGE_PREFIX)
@@ -53,7 +54,6 @@ define Device/avnet_zynq-zed
 	$(call Device/FitImageGzip)
 	DEVICE_VENDOR := Avnet
 	DEVICE_MODEL := ZedBoard
-	DEVICE_DTS := zynq-zed
 endef
 TARGET_DEVICES += avnet_zynq-zed
 
@@ -61,7 +61,6 @@ define Device/digilent_zynq-zybo
 	$(call Device/FitImageGzip)
 	DEVICE_VENDOR := Digilent
 	DEVICE_MODEL := Zybo
-	DEVICE_DTS := zynq-zybo
 endef
 TARGET_DEVICES += digilent_zynq-zybo
 
@@ -69,7 +68,6 @@ define Device/digilent_zynq-zybo-z7
 	$(call Device/FitImageGzip)
 	DEVICE_VENDOR := Digilent
 	DEVICE_MODEL := Zybo Z7
-	DEVICE_DTS := zynq-zybo-z7
 endef
 TARGET_DEVICES += digilent_zynq-zybo-z7
 
@@ -77,7 +75,6 @@ define Device/xlnx_zynq-zc702
 	$(call Device/FitImageGzip)
 	DEVICE_VENDOR := Xilinx
 	DEVICE_MODEL := ZC702
-	DEVICE_DTS := zynq-zc702
 	DEVICE_PACKAGES:=kmod-can kmod-can-xilinx-can
 endef
 TARGET_DEVICES += xlnx_zynq-zc702