[MIPS] page.h: remove __pa() usages.

__pa() was used by virt_to_page() and virt_addr_valid(). These
latter are used when kernel is initialised so __pa() is not
appropriate, we use virt_to_phys() instead.

Futhermore __pa() is going to take care of CKSEG0/XKPHYS
address mix for 64 bit kernels. This makes __pa() more complex
than virt_to_phys() and this extra work is not needed by
virt_to_page() and virt_addr_valid().

Eventually it consolidates virt_to_phys() prototype by making
its argument 'const'. this avoids some warnings that was due
to some virt_to_page() usages which pass const pointer.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/pgtable.h b/include/asm-mips/pgtable.h
index 1ca4d1e..f2e1325 100644
--- a/include/asm-mips/pgtable.h
+++ b/include/asm-mips/pgtable.h
@@ -67,7 +67,7 @@
 extern unsigned long zero_page_mask;
 
 #define ZERO_PAGE(vaddr) \
-	(virt_to_page(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask)))
+	(virt_to_page((void *)(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask))))
 
 #define __HAVE_ARCH_MOVE_PTE
 #define move_pte(pte, prot, old_addr, new_addr)				\