powerpc: Fix booting P9 hash with CONFIG_PPC_RADIX_MMU=N

Currently if you disable CONFIG_PPC_RADIX_MMU you'll crash on boot on
a P9. This is because we still set MMU_FTR_TYPE_RADIX via
ibm,pa-features and MMU_FTR_TYPE_RADIX is what's used for code patching
in much of the asm code (ie. slb_miss_realmode)

This patch fixes the problem by stopping MMU_FTR_TYPE_RADIX from being
set from ibm.pa-features.

We may eventually end up removing the CONFIG_PPC_RADIX_MMU option
completely but until then this fixes the issue.

Fixes: 17a3dd2f5fc7 ("powerpc/mm/radix: Use firmware feature to enable Radix MMU")
Cc: stable@vger.kernel.org # v4.7+
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/prom.c

@@ -161,7 +161,9 @@ static struct ibm_pa_feature {
 	{ .pabyte = 0,  .pabit = 3, .cpu_features  = CPU_FTR_CTRL },
 	{ .pabyte = 0,  .pabit = 6, .cpu_features  = CPU_FTR_NOEXECUTE },
 	{ .pabyte = 1,  .pabit = 2, .mmu_features  = MMU_FTR_CI_LARGE_PAGE },
+#ifdef CONFIG_PPC_RADIX_MMU
 	{ .pabyte = 40, .pabit = 0, .mmu_features  = MMU_FTR_TYPE_RADIX },
+#endif
 	{ .pabyte = 1,  .pabit = 1, .invert = 1, .cpu_features = CPU_FTR_NODSISRALIGN },
 	{ .pabyte = 5,  .pabit = 0, .cpu_features  = CPU_FTR_REAL_LE,
 				    .cpu_user_ftrs = PPC_FEATURE_TRUE_LE },