parisc: fix kernel BUG at arch/parisc/include/asm/mmzone.h:50 (part 2)

Make sure that we really return -1 (instead of 0x00ff) as node id for
page frame numbers which are not physically available.

This finally fixes the kernel panic when running
cat /proc/kpageflags /proc/kpagecount.

Theoretically this patch now limits the number of physical memory ranges
to 127 instead of 254, but currently we have MAX_PHYSMEM_RANGES
hardcoded to 8 which is sufficient for all existing parisc machines.

Signed-off-by: Helge Deller <deller@gmx.de>
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 1c96564..505b56c 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -47,7 +47,7 @@
 
 #ifdef CONFIG_DISCONTIGMEM
 struct node_map_data node_data[MAX_NUMNODES] __read_mostly;
-unsigned char pfnnid_map[PFNNID_MAP_MAX] __read_mostly;
+signed char pfnnid_map[PFNNID_MAP_MAX] __read_mostly;
 #endif
 
 static struct resource data_resource = {