package/open62541: disable Events when Namespace is minimal

The option UA_ENABLE_SUBSCRIPTIONS_EVENTS is enabled by default,
but not compatible with UA_NAMESPACE_ZERO=MINIMAL resulting in

CMake Error at CMakeLists.txt:1120 (message):
  Events require at least the reduced Namespace Zero

Fixes: http://autobuild.buildroot.net/results/d8e34b8bddf0f3568e64705c6618b17bce70d210/

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/open62541/open62541.mk

@@ -34,7 +34,7 @@ OPEN62541_CONF_OPTS += -DUA_ENABLE_ENCRYPTION=OPENSSL
 endif
 
 ifeq ($(BR2_PACKAGE_OPEN62541_UA_NAMESPACE_ZERO_MINIMAL),y)
-OPEN62541_CONF_OPTS += -DUA_NAMESPACE_ZERO=MINIMAL
+OPEN62541_CONF_OPTS += -DUA_NAMESPACE_ZERO=MINIMAL -DUA_ENABLE_SUBSCRIPTIONS_EVENTS=OFF
 else ifeq ($(BR2_PACKAGE_OPEN62541_UA_NAMESPACE_ZERO_REDUCED),y)
 OPEN62541_CONF_OPTS += -DUA_NAMESPACE_ZERO=REDUCED
 else ifeq ($(BR2_PACKAGE_OPEN62541_UA_NAMESPACE_ZERO_FULL),y)