libnvdimm/region: Fix build error

On CONFIG_PPC32=y build fails:

drivers/nvdimm/region_devs.c:1034:14: note: in expansion of macro ‘do_div’
  remainder = do_div(per_mapping, mappings);
              ^~~~~~
In file included from ./arch/powerpc/include/generated/asm/div64.h:1:0,
                 from ./include/linux/kernel.h:18,
                 from ./include/asm-generic/bug.h:19,
                 from ./arch/powerpc/include/asm/bug.h:109,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/scatterlist.h:7,
                 from drivers/nvdimm/region_devs.c:5:
./include/asm-generic/div64.h:243:22: error: passing argument 1 of ‘__div64_32’ from incompatible pointer type [-Werror=incompatible-pointer-types]
   __rem = __div64_32(&(n), __base); \

Use div_u64 instead of do_div to fix this.

Fixes: 2522afb8 ("libnvdimm/region: Introduce an 'align' attribute")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200331115024.31628-1-yuehaibing@huawei.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/region_devs.c

@@ -563,8 +563,7 @@ static ssize_t align_store(struct device *dev,
 	 * contribute to the tail capacity in system-physical-address
 	 * space for the namespace.
 	 */
-	dpa = val;
-	remainder = do_div(dpa, nd_region->ndr_mappings);
+	dpa = div_u64_rem(val, nd_region->ndr_mappings, &remainder);
 	if (!is_power_of_2(dpa) || dpa < PAGE_SIZE
 			|| val > region_size(nd_region) || remainder)
 		return -EINVAL;
@@ -1010,7 +1009,7 @@ EXPORT_SYMBOL(nd_region_release_lane);
 
 static unsigned long default_align(struct nd_region *nd_region)
 {
-	unsigned long align, per_mapping;
+	unsigned long align;
 	int i, mappings;
 	u32 remainder;
 
@@ -1030,8 +1029,7 @@ static unsigned long default_align(struct nd_region *nd_region)
 	}
 
 	mappings = max_t(u16, 1, nd_region->ndr_mappings);
-	per_mapping = align;
-	remainder = do_div(per_mapping, mappings);
+	div_u64_rem(align, mappings, &remainder);
 	if (remainder)
 		align *= mappings;