selftests:prctl: Fix make clean override warning

Remove clean target in Makefile to fix the following warning
and use the one in common lib.mk

Makefile:14: warning: overriding recipe for target 'clean'
../lib.mk:160: warning: ignoring old recipe for target 'clean'

Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/prctl/Makefile

···
 
 include ../lib.mk
 
-clean:
-	rm -fr $(TEST_PROGS)
 endif
 endif