ramips: fix Asus RT-N56U dts filename

Other Asus RT-N dts files are named "RT-N..." (not "RTN..."), so use the same for RT-N56U.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

SVN-Revision: 46619

target/linux/ramips/image/Makefile

@@ -819,12 +819,12 @@ omniembhpm_mtd_size=16449536
 Image/Build/Profile/OMNIEMBHPM=$(call BuildFirmware/CustomFlash/$(1),$(1),omni-emb-hpm,OMNI-EMB-HPM,$(omniembhpm_mtd_size))
 
 define BuildFirmware/RTN56U/squashfs
-	$(call BuildFirmware/Default8M/$(1),$(1),rt-n56u,RTN56U)
+	$(call BuildFirmware/Default8M/$(1),$(1),rt-n56u,RT-N56U)
 	-mkrtn56uimg -s $(call sysupname,$(1),rt-n56u)
 	-cp $(call sysupname,$(1),rt-n56u) $(call imgname,$(1),rt-n56u)-factory.bin
 	-mkrtn56uimg -f $(call imgname,$(1),rt-n56u)-factory.bin
 endef
-Image/Build/Profile/RTN56U=$(call BuildFirmware/RTN56U/$(1),$(1),rt-n56u,RTN56U)
+Image/Build/Profile/RTN56U=$(call BuildFirmware/RTN56U/$(1),$(1),rt-n56u,RT-N56U)
 
 Image/Build/Profile/TEW691GR=$(call BuildFirmware/UMedia/$(1),$(1),tew-691gr,TEW-691GR,0x026910)