dtc: fix project and download url

This fix the error:

fatal: unable to connect to git.jdl.com:
git.jdl.com[0: 208.123.73.151]: errno=Connection refused

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/dtc/Config.in

@@ -8,7 +8,7 @@ config BR2_PACKAGE_DTC
 	  Note that only the library is installed.
 	  If you want the programs, say 'y' here, and to "dtc programs", below.
 
-	  http://git.jdl.com/gitweb/?p=dtc.git  (no home page)
+	  https://git.kernel.org/cgit/utils/dtc/dtc.git
 
 if BR2_PACKAGE_DTC
 

package/dtc/dtc.mk

@@ -4,8 +4,9 @@
 #
 ################################################################################
 
-DTC_VERSION = v1.4.0
-DTC_SITE = git://git.jdl.com/software/dtc.git
+DTC_VERSION = 1.4.0
+DTC_SOURCE = dtc-$(DTC_VERSION).tar.xz
+DTC_SITE = https://www.kernel.org/pub/software/utils/dtc
 DTC_LICENSE = GPLv2+/BSD-2c
 DTC_LICENSE_FILES = README.license GPL
 DTC_INSTALL_STAGING = YES