[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/io.h b/include/asm-mips/io.h
index bc5f3c5..d77b657 100644
--- a/include/asm-mips/io.h
+++ b/include/asm-mips/io.h
@@ -113,7 +113,7 @@
  *     almost all conceivable cases a device driver should not be using
  *     this function
  */
-static inline unsigned long virt_to_phys(volatile void * address)
+static inline unsigned long virt_to_phys(volatile const void *address)
 {
 	return (unsigned long)address - PAGE_OFFSET;
 }