include/asm-xtensa/io.h must #include <asm/page.h>

This patch fixes the following compile error with
-Werror-implicit-function-declaration:

<-- snip -->

...
CC kernel/time/clocksource.o
In file included from /home/bunk/linux/kernel-2.6/linux-2.6.22-rc6-mm1/include/linux/clocksource.h:18,
from
/home/bunk/linux/kernel-2.6/linux-2.6.22-rc6-mm1/kernel/time/clocksource.c:27:
include2/asm/io.h: In function 'virt_to_phys':
include2/asm/io.h:46: error: implicit declaration of function '__pa' include2/asm/io.h: In function 'phys_to_virt':
include2/asm/io.h:51: error: implicit declaration of function '__va' include2/asm/io.h:51: warning: return makes pointer from integer without a cast make[3]: *** [kernel/time/clocksource.o] Error 1

<-- snip -->

---

@@ -13,6 +13,7 @@
 
 #ifdef __KERNEL__
 #include <asm/byteorder.h>
+#include <asm/page.h>
 
 #include <linux/types.h>