ibrdtn: fix bogus dependency on zlib

Due to a copy/paste mistake, zlib was being added to
<pkg>_DEPENDENCIES even when not enabled in the configuration. This
commit fixes that.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/ibrdtn/ibrdtn.mk

@@ -17,7 +17,6 @@ IBRDTN_CONF_OPTS += --with-compression
 IBRDTN_DEPENDENCIES += zlib
 else
 IBRDTN_CONF_OPTS += --without-compression
-IBRDTN_DEPENDENCIES += zlib
 endif
 
 ifeq ($(BR2_PACKAGE_LIBGLIB2),y)