powerpc/dt_cpu_ftrs: Enable Prefixed Instructions

Prefix instructions have their own FSCR bit which needs to be enabled
via a CPU feature. The kernel will save the FSCR for problem state but
it needs to be enabled initially.
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200521014341.29095-6-alistair@popple.id.au

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -634,6 +634,7 @@ static struct dt_cpu_feature_match __initdata
 	{"vector-binary128", feat_enable, 0},
 	{"vector-binary16", feat_enable, 0},
 	{"wait-v3", feat_enable, 0},
+	{"prefix-instructions", feat_enable, 0},
 };
 
 static bool __initdata using_dt_cpu_ftrs;