fix compilation error in include/asm/prom.h

make defconfig give the following error on ppc (gcc-4):

arch/ppc/syslib/prom_init.c:120: error: static declaration of ‘prom_display_paths’ follows non-static declaration include/asm/prom.h:17: error: previous declaration of ‘prom_display_paths’ was here arch/ppc/syslib/prom_init.c:122: error: static declaration of ‘prom_num_displays’ follows non-static declaration include/asm/prom.h:18: error: previous declaration of ‘prom_num_displays’ was here

The following patch solves it.

@@ -14,9 +14,6 @@
 typedef u32 phandle;
 typedef u32 ihandle;
 
-extern char *prom_display_paths[];
-extern unsigned int prom_num_displays;
-
 struct address_range {
 	unsigned int space;
 	unsigned int address;