nfs: fix a minor do_div portability issue

This change modifies filelayout_get_dense_offset() to use the functions
in math64.h and thus avoid a 32-bit platform compile error trying to
use do_div() on an s64 type.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Reviewed-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -49,13 +49,14 @@ filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
 			    loff_t offset)
 {
 	u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
-	u64 tmp;
+	u64 stripe_no;
+	u32 rem;
 
 	offset -= flseg->pattern_offset;
-	tmp = offset;
-	do_div(tmp, stripe_width);
+	stripe_no = div_u64(offset, stripe_width);
+	div_u64_rem(offset, flseg->stripe_unit, &rem);
 
-	return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
+	return stripe_no * flseg->stripe_unit + rem;
 }
 
 /* This function is used by the layout driver to calculate the