selftests/memory-hotplug: Remove the redundant warning information

Remove the redundant warning information of online_all_offline_memory()
since there is a warning in online_memory_expect_success().

Signed-off-by: Zhao Gongyi <zhaogongyi@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/memory-hotplug/mem-on-off-test.sh

@@ -138,7 +138,6 @@ online_all_offline_memory()
 {
 	for memory in `hotpluggable_offline_memory`; do
 		if ! online_memory_expect_success $memory; then
-			echo "$FUNCNAME $memory: unexpected fail" >&2
 			retval=1
 		fi
 	done