MIPS: page.h: Define virt_to_pfn()

Define virt_to_pfn() based on the existing definition of virt_to_page()
which already does a PFN_DOWN(vir_to_phys(kaddr)).
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15409/Signed-off-by: James Hogan <jhogan@kernel.org>

arch/mips/include/asm/page.h

@@ -240,8 +240,8 @@ static inline int pfn_valid(unsigned long pfn)
 
 #endif
 
-#define virt_to_page(kaddr)	pfn_to_page(PFN_DOWN(virt_to_phys((void *)     \
-								  (kaddr))))
+#define virt_to_pfn(kaddr)   	PFN_DOWN(virt_to_phys((void *)(kaddr)))
+#define virt_to_page(kaddr)	pfn_to_page(virt_to_pfn(kaddr))
 
 extern int __virt_addr_valid(const volatile void *kaddr);
 #define virt_addr_valid(kaddr)						\