wireless-regdb: use BR2_KERNEL_MIRROR for download site

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

package/wireless-regdb/wireless-regdb.mk

@@ -6,7 +6,7 @@
 
 WIRELESS_REGDB_VERSION = 2018.09.07
 WIRELESS_REGDB_SOURCE = wireless-regdb-$(WIRELESS_REGDB_VERSION).tar.xz
-WIRELESS_REGDB_SITE = http://kernel.org/pub/software/network/wireless-regdb
+WIRELESS_REGDB_SITE = $(BR2_KERNEL_MIRROR)/software/network/wireless-regdb
 WIRELESS_REGDB_LICENSE = ISC
 WIRELESS_REGDB_LICENSE_FILES = LICENSE