selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround

alignment_handler currently only tests the unaligned cases but it can
also be useful for testing the workaround for the P9N DD2.1 vector CI
load issue fixed by p9_hmi_special_emu(). This workaround was
introduced in 5080332c ("powerpc/64s: Add workaround for P9 vector
CI load issue").

This changes the loop to start from offset 0 rather than 1 so that we
test the kernel emulation in p9_hmi_special_emu().
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201013043741.743413-2-mikey@neuling.org

tools/testing/selftests/powerpc/alignment/alignment_handler.c

@@ -266,8 +266,12 @@ int do_test(char *test_name, void (*test_func)(char *, char *))
 	}
 
 	rc = 0;
-	/* offset = 0 no alignment fault, so skip */
-	for (offset = 1; offset < 16; offset++) {
+	/*
+	 * offset = 0 is aligned but tests the workaround for the P9N
+	 * DD2.1 vector CI load issue (see 5080332c2c89 "powerpc/64s:
+	 * Add workaround for P9 vector CI load issue")
+	 */
+	for (offset = 0; offset < 16; offset++) {
 		width = 16; /* vsx == 16 bytes */
 		r = 0;