tests/Makefile: Fix inclusion of the qos dependency files

The qos dependency files can be found under tests/qtest/libqos and
not under tests/qtest/qos.

Fixes: 1cf4323e ("Move the libqos files under tests/qtest/")
Message-Id: <20200127140245.20065-1-thuth@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>

tests/Makefile.include

@@ -919,6 +919,6 @@ all: $(QEMU_IOTESTS_HELPERS-y)
 
 -include $(wildcard tests/*.d)
 -include $(wildcard tests/qtest/*.d)
--include $(wildcard tests/qtest/qos/*.d)
+-include $(wildcard tests/qtest/libqos/*.d)
 
 endif