[POWERPC] Size swapper_pg_dir correctly

David Gibson pointed out that swapper_pg_dir actually need to be
PGD_TABLE_SIZE bytes long not PAGE_SIZE.  This actually saves 64k in
the bss for a kernel ppc64_defconfig built with CONFIG_PPC_64K_PAGES.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/asm-offsets.c

@@ -320,5 +320,9 @@ int main(void)
 	DEFINE(VMALLOC_START_ESID, GET_ESID(VMALLOC_START));
 	DEFINE(VMALLOC_START_VSID, KERNEL_VSID(VMALLOC_START));
 #endif
+
+#ifdef CONFIG_PPC64
+	DEFINE(PGD_TABLE_SIZE, PGD_TABLE_SIZE);
+#endif
 	return 0;
 }