Revert "selftests/powerpc: Fix out-of-tree build errors"

This reverts commit d8a2fe29d3.

That commit, by me, fixed the out of tree build errors by causing some
of the tests not to build at all.

tools/testing/selftests/powerpc/cache_shape/Makefile

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 TEST_PROGS := cache_shape
 
+all: $(TEST_PROGS)
+
 $(TEST_PROGS): ../harness.c ../utils.c
 
 top_srcdir = ../../../../..