selftests/powerpc: Sort the list of SUB_DIRS to build

This list has gotten too long. Split it into individual lines and sort
them, so in future we can add new entries more cleanly.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
index b120dc1..0c2706b 100644
--- a/tools/testing/selftests/powerpc/Makefile
+++ b/tools/testing/selftests/powerpc/Makefile
@@ -12,7 +12,17 @@
 
 export CFLAGS
 
-SUB_DIRS = pmu copyloops mm tm primitives stringloops vphn switch_endian dscr benchmarks syscalls
+SUB_DIRS = benchmarks 		\
+	   copyloops		\
+	   dscr			\
+	   mm			\
+	   pmu			\
+	   primitives		\
+	   stringloops		\
+	   switch_endian	\
+	   syscalls		\
+	   tm			\
+	   vphn
 
 endif