Fasm plugin: Use common plugin test Makefile

Signed-off-by: Tomasz Michalak <tmichalak@antmicro.com>
diff --git a/fasm-plugin/tests/Makefile b/fasm-plugin/tests/Makefile
index f5ddc62..320dfcf 100644
--- a/fasm-plugin/tests/Makefile
+++ b/fasm-plugin/tests/Makefile
@@ -1,6 +1 @@
-TESTS = dummy
-
-all: $(TESTS)
-
-dummy:
-	@echo $@ PASS
+include $(shell pwd)/../../Makefile_test.common