package/collectd: rename --with-yajl

--with-yajl is not recognized so replace it by the correct
--with-libyajl option

The option is named --with-libyajl since a very long time (since at
least version 4.8.0 and
https://github.com/collectd/collectd/commit/f154fb21fbb1fee2f2262d421eca32e7e340f420)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/collectd/collectd.mk

@@ -202,7 +202,7 @@ COLLECTD_CONF_OPTS += --with-libpq=$(STAGING_DIR)/usr/bin/pg_config
 COLLECTD_CONF_ENV += LIBS="-lpthread -lm"
 endif
 ifeq ($(BR2_PACKAGE_YAJL),y)
-COLLECTD_CONF_OPTS += --with-yajl=$(STAGING_DIR)/usr
+COLLECTD_CONF_OPTS += --with-libyajl=$(STAGING_DIR)/usr
 endif
 
 # network can use libgcrypt