payloads/depthcharge: Fix clean target

This line has a weird history. It got a `|| exit 0` removed lately which
obviously was there to fix the presence of the superfluous `test` at the
beginning. Now, remove the `test` too to make the clean target always
succeed again ;)

Change-Id: I9e069cf5d9ac8416cf350161439aa60798ef7b6b
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20769
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

payloads/external/depthcharge/Makefile

@@ -89,7 +89,7 @@ build: config
 		PATH="$(abspath ../../../build/util/cbfstool):$$PATH"
 
 clean:
-	test -d $(output_dir) && rm -rf $(output_dir)
+	rm -rf $(output_dir)
 
 distclean:
 	rm -rf $(project_dir)