powerpc/32s: get rid of CPU_FTR_601 feature

Now that 601 is exclusive from other 6xx, CPU_FTR_601 and
associated fixups are useless.

Drop this feature and use #ifdefs instead.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/ecdb7194a17dbfa01865df6a82979533adc2c70b.1566834712.git.christophe.leroy@c-s.fr

arch/powerpc/mm/ptdump/bats.c

@@ -149,7 +149,7 @@ static int bats_show_603(struct seq_file *m, void *v)
 
 static int bats_open(struct inode *inode, struct file *file)
 {
-	if (cpu_has_feature(CPU_FTR_601))
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S_601))
 		return single_open(file, bats_show_601, NULL);
 
 	return single_open(file, bats_show_603, NULL);