selftests/powerpc: Update PROT_SAO test to skip ISA 3.1

Since SAO support was removed from ISA 3.1, skip the
prot_sao test if PPC_FEATURE2_ARCH_3_1 is set.
Signed-off-by: Shawn Anastasio <shawn@anastas.io>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200821185558.35561-4-shawn@anastas.io

tools/testing/selftests/powerpc/mm/prot_sao.c

@@ -18,8 +18,9 @@ int test_prot_sao(void)
 {
 	char *p;
 
-	/* 2.06 or later should support SAO */
-	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06));
+	/* SAO was introduced in 2.06 and removed in 3.1 */
+	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06) ||
+		have_hwcap2(PPC_FEATURE2_ARCH_3_1));
 
 	/*
 	 * Ensure we can ask for PROT_SAO.