sh: __uncached_start only on sh32.

sh64 doesn't provide __uncached_start, so don't reference it
unconditionally.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/mm/init.c

@@ -203,6 +203,7 @@ void __init paging_init(void)
 
 	free_area_init_nodes(max_zone_pfns);
 
+#ifdef CONFIG_SUPERH32
 	/* Set up the uncached fixmap */
 	set_fixmap_nocache(FIX_UNCACHED, __pa(&__uncached_start));
 
@@ -214,6 +215,7 @@ void __init paging_init(void)
 	 */
 	cached_to_uncached = P2SEG - P1SEG;
 #endif
+#endif
 }
 
 static struct kcore_list kcore_mem, kcore_vmalloc;