package/flannel: use the github helper

Currently, flannel uses an ad-hoc github URL and a version-only tarball
name, even though we already had the github helper (introduced in 2013)
when flannel was introduced (in 2016).

Switch to the github helper, which allows us to get a properly named
tarball.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Geoff Levand <geoff@infradead.org>
Acked-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/flannel/flannel.hash

@@ -1,3 +1,3 @@
 # Locally computed:
-sha256  e17164db3b158d13ce5e40bb7b233790cb186762d929fa4f626baf586d4d63ca  v0.14.0.tar.gz
+sha256  e17164db3b158d13ce5e40bb7b233790cb186762d929fa4f626baf586d4d63ca  flannel-0.14.0.tar.gz
 sha256  cfc7749b96f63bd31c3c42b5c471bf756814053e847c10f3eb003417bc523d30  LICENSE

package/flannel/flannel.mk

@@ -5,8 +5,7 @@
 ################################################################################
 
 FLANNEL_VERSION = 0.14.0
-FLANNEL_SITE = https://github.com/flannel-io/flannel/archive
-FLANNEL_SOURCE = v$(FLANNEL_VERSION).tar.gz
+FLANNEL_SITE = $(call github,flannel-io,flannel,v$(FLANNEL_VERSION))
 
 FLANNEL_LICENSE = Apache-2.0
 FLANNEL_LICENSE_FILES = LICENSE