powerpc: Update documentation for noltlbs kernel parameter

Now the noltlbs kernel parameter is also applicable to PPC8xx
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <oss@buserror.net>

Documentation/kernel-parameters.txt

@@ -2582,7 +2582,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
 
 	noltlbs		[PPC] Do not use large page/tlb entries for kernel
-			lowmem mapping on PPC40x.
+			lowmem mapping on PPC40x and PPC8xx
 
 	nomca		[IA-64] Disable machine check abort handling