ARM: fix type of PHYS_PFN_OFFSET to unsigned long

On LPAE machines, PHYS_OFFSET evaluates to a phys_addr_t and this type is
inherited by the PHYS_PFN_OFFSET definition as well.  Consequently, the kernel
build emits warnings of the form:

init/main.c: In function 'start_kernel':
init/main.c:588:7: warning: format '%lx' expects argument of type 'long unsigned int', but argument 2 has type 'phys_addr_t' [-Wformat]

This patch fixes this warning by pinning down the PFN type to unsigned long.
Signed-off-by: NCyril Chemparathy <cyril@ti.com>
Acked-by: NNicolas Pitre <nico@linaro.org>
Tested-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: NSubash Patel <subash.rp@samsung.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm/include/asm/memory.h

@@ -223,7 +223,7 @@ static inline unsigned long __phys_to_virt(unsigned long x)
  * direct-mapped view.  We assume this is the first page
  * of RAM in the mem_map as well.
  */
-#define PHYS_PFN_OFFSET	(PHYS_OFFSET >> PAGE_SHIFT)
+#define PHYS_PFN_OFFSET	((unsigned long)(PHYS_OFFSET >> PAGE_SHIFT))
 
 /*
  * These are *only* valid on the kernel direct mapped RAM memory.