powerpc: Remove CONFIG_POWER3

Now that we have dropped power3 support we can remove CONFIG_POWER3. The
usage in pgtable_32.c was already dead code as CONFIG_POWER3 was not
selectable on PPC32.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/pgtable_32.c

@@ -41,7 +41,7 @@ unsigned long ioremap_base;
 unsigned long ioremap_bot;
 EXPORT_SYMBOL(ioremap_bot);	/* aka VMALLOC_END */
 
-#if defined(CONFIG_6xx) || defined(CONFIG_POWER3)
+#ifdef CONFIG_6xx
 #define HAVE_BATS	1
 #endif