libeXosip2: remove redundant LIBOSIP2_SOURCE definition

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libeXosip2/libeXosip2.mk

@@ -5,7 +5,6 @@
 #############################################################
 
 LIBEXOSIP2_VERSION = 3.6.0
-LIBEXOSIP2_SOURCE = libeXosip2-$(LIBEXOSIP2_VERSION).tar.gz
 LIBEXOSIP2_SITE = http://download.savannah.gnu.org/releases/exosip/
 LIBEXOSIP2_INSTALL_STAGING = YES