powerpc/64s: Fix pkey support in dt_cpu_ftrs, add CPU_FTR_PKEY bit

The pkey code added a CPU_FTR_PKEY bit, but did not add it to the
dt_cpu_ftrs feature set. Although capability is supported by all
processors in the base dt_cpu_ftrs set for 64s, it's a significant
and sufficiently well defined feature to make it optional. So add
it as a quirk for now, which can be versioned out then controlled
by the firmware (once dt_cpu_ftrs gains versioning support).

Fixes: cf43d3b26452 ("powerpc: Enable pkey subsystem")
Cc: stable@vger.kernel.org # v4.16+
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -729,6 +729,13 @@ static __init void cpufeatures_cpu_quirks(void)
 		cur_cpu_spec->cpu_features &= ~(CPU_FTR_DAWR);
 		cur_cpu_spec->cpu_features |= CPU_FTR_P9_TLBIE_BUG;
 	}
+
+	/*
+	 * PKEY was not in the initial base or feature node
+	 * specification, but it should become optional in the next
+	 * cpu feature version sequence.
+	 */
+	cur_cpu_spec->cpu_features |= CPU_FTR_PKEY;
 }
 
 static void __init cpufeatures_setup_finished(void)