powerpc/ptdump: get out of note_prot_wx() when CONFIG_PPC_DEBUG_WX is not selected.

When CONFIG_PPC_DEBUG_WX, note_prot_wx() is useless.

Get out of it early and inconditionnally in that case,
so that GCC can kick all the code out.
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/ff6c8f631bd4ce3a10e0cc241eb569816187bc20.1565786091.git.christophe.leroy@c-s.fr

arch/powerpc/mm/ptdump/ptdump.c

@@ -177,7 +177,7 @@ static void dump_addr(struct pg_state *st, unsigned long addr)
 
 static void note_prot_wx(struct pg_state *st, unsigned long addr)
 {
-	if (!st->check_wx)
+	if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx)
 		return;
 
 	if (!((st->current_flags & pgprot_val(PAGE_KERNEL_X)) == pgprot_val(PAGE_KERNEL_X)))