tools/testing/selftests/Makefile: alphasort the TARGETS list

This list is supposed to be sorted, to reduce patch collisions.

Cc: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>