[MIPS] Add external declaration of pagetable_init() to pgalloc.h

This fixes some sparse warnings.

pgtable-32.c:15:6: warning: symbol 'pgd_init' was not declared. Should it be static?
pgtable-32.c:32:13: warning: symbol 'pagetable_init' was not declared. Should it be static?

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/sgi-ip27/ip27-memory.c

diff --git a/arch/mips/sgi-ip27/ip27-memory.c b/arch/mips/sgi-ip27/ip27-memory.c
index 0e3d535..fe8a106 100644
--- a/arch/mips/sgi-ip27/ip27-memory.c
+++ b/arch/mips/sgi-ip27/ip27-memory.c
@@ -21,6 +21,7 @@
 #include <linux/pfn.h>
 #include <linux/highmem.h>
 #include <asm/page.h>
+#include <asm/pgalloc.h>
 #include <asm/sections.h>
 
 #include <asm/sn/arch.h>
@@ -503,7 +504,6 @@
 	/* We got nothing to free here ...  */
 }
 
-extern void pagetable_init(void);
 extern unsigned long setup_zero_pages(void);
 
 void __init paging_init(void)