PM: hibernate: improve arithmetic division in preallocate_highmem_fraction()

do_div() does a 64-by-32 division. Use div64_u64() instead of
do_div() if the divisor is u64, to avoid truncation to 32-bit.

This change also cleans up code a tad.
Signed-off-by: NWen Yang <wenyang@linux.alibaba.com>
[ rjw: Subject ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/snapshot.c

@@ -1566,9 +1566,7 @@ static unsigned long preallocate_image_highmem(unsigned long nr_pages)
  */
 static unsigned long __fraction(u64 x, u64 multiplier, u64 base)
 {
-	x *= multiplier;
-	do_div(x, base);
-	return (unsigned long)x;
+	return div64_u64(x * multiplier, base);
 }
 
 static unsigned long preallocate_highmem_fraction(unsigned long nr_pages,