xenomai: update download site

The new address include more recent versions of stable releases.
Therefore, newer versions than 2.6.4 can be available when required.

Signed-off-by: Erdem MEYDANLI <erdem.meydanli@punica.com.tr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/xenomai/xenomai.mk

@@ -11,7 +11,7 @@ else
 BR_NO_CHECK_HASH_FOR += $(XENOMAI_SOURCE)
 endif
 
-XENOMAI_SITE = http://download.gna.org/xenomai/stable
+XENOMAI_SITE = https://xenomai.org/downloads/xenomai/stable
 XENOMAI_SOURCE = xenomai-$(XENOMAI_VERSION).tar.bz2
 XENOMAI_LICENSE = headers: GPLv2+ with exception, libraries: LGPLv2.1+, kernel: GPLv2+, docs: GFDLv1.2+, ipipe patch and can driver: GPLv2
 # GFDL is not included but refers to gnu.org