selftests: Add install support for the powerpc tests

The bulk of the selftests are actually below the powerpc sub directory.

This adds support for installing them, when on a powerpc machine, or if
ARCH and CROSS_COMPILE are set appropriately.

This is a little more complicated because of the sub directory structure
under powerpc, but much of the common logic in lib.mk is still used. The
net effect of the patch is still a reduction in code.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/powerpc/primitives/Makefile

@@ -1,17 +1,12 @@
 CFLAGS += -I$(CURDIR)
 
-PROGS := load_unaligned_zeropad
+TEST_PROGS := load_unaligned_zeropad
 
-all: $(PROGS)
+all: $(TEST_PROGS)
 
-$(PROGS): ../harness.c
+$(TEST_PROGS): ../harness.c
 
-run_tests: all
-	@-for PROG in $(PROGS); do \
-		./$$PROG; \
-	done;
+include ../../lib.mk
 
 clean:
-	rm -f $(PROGS) *.o
-
-.PHONY: all run_tests clean
+	rm -f $(TEST_PROGS) *.o