/dev/mem: Use more consistent data types

The xlate_dev_{kmem,mem}_ptr() functions take either a physical address
or a kernel virtual address, so data types should be phys_addr_t and
void *. They both return a kernel virtual address which is only ever
used in calls to copy_{from,to}_user(), so make variables that store it
void * rather than char * for consistency.

Also only define a weak unxlate_dev_mem_ptr() function if architectures
haven't overridden them in the asm/io.h header file.

Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/s390/mm/maccess.c

@@ -176,7 +176,7 @@ static int is_swapped(unsigned long addr)
  * For swapped prefix pages a new buffer is returned that contains a copy of
  * the absolute memory. The buffer size is maximum one page large.
  */
-void *xlate_dev_mem_ptr(unsigned long addr)
+void *xlate_dev_mem_ptr(phys_addr_t addr)
 {
 	void *bounce = (void *) addr;
 	unsigned long size;
@@ -197,7 +197,7 @@ void *xlate_dev_mem_ptr(unsigned long addr)
 /*
  * Free converted buffer for /dev/mem access (if necessary)
  */
-void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
+void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 {
 	if ((void *) addr != buf)
 		free_page((unsigned long) buf);