Introduce virt_to_phys()

virt_to_phys() returns the physical address given a virtual. In most
cases this will be just the input value as the vast majority of
systems run in a 1:1 mode.

However in systems that are not running this way it should report the
physical address or ~0 if no mapping exists for the given virtual
address.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/asm-mips/io.h b/include/asm-mips/io.h
index 3a0f33f..031186d 100644
--- a/include/asm-mips/io.h
+++ b/include/asm-mips/io.h
@@ -118,7 +118,7 @@
  * Change virtual addresses to physical addresses and vv.
  * These are trivial on the 1:1 Linux/MIPS mapping
  */
-extern inline unsigned long virt_to_phys(volatile void * address)
+extern inline phys_addr_t virt_to_phys(void * address)
 {
 	return CPHYSADDR(address);
 }