hw/test: include -gcov binaries in clean target

This patch fixes an oversight in the hw-clean make target that removes the
.gcno object, but does not remove the -gcovr test binary. Therefore, the
.gcno object is not recreated on a subsequent coverage-report build,
which causes an error that fails the build.

Signed-off-by: Eric Richter <erichte@linux.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

hw/test/Makefile.check

@@ -26,4 +26,4 @@ $(HW_TEST:%=%-gcov): %-gcov : %.c %
 clean: hw-clean
 
 hw-clean:
-	$(RM) -f hw/test/*.[od] $(HW_TEST)
+	$(RM) -f hw/test/*.[od] $(HW_TEST) $(HW_TEST:%=%-gcov)