[XFS] Fix incorrect use of do_div on realtime device growfs code path.

SGI Modid: xfs-linux:xfs-kern:178670a
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/xfs_rtalloc.c

@@ -1966,7 +1966,8 @@ xfs_growfs_rt(
 	/*
 	 * Calculate new parameters.  These are the final values to be reached.
 	 */
-	nrextents = do_div(nrblocks, in->extsize);
+	nrextents = nrblocks;
+	do_div(nrextents, in->extsize);
 	nrbmblocks = roundup_64(nrextents, NBBY * sbp->sb_blocksize);
 	nrextslog = xfs_highbit32(nrextents);
 	nrsumlevels = nrextslog + 1;
@@ -2021,7 +2022,8 @@ xfs_growfs_rt(
 			XFS_RTMIN(nrblocks,
 				  nsbp->sb_rbmblocks * NBBY *
 				  nsbp->sb_blocksize * nsbp->sb_rextsize);
-		nsbp->sb_rextents = do_div(nsbp->sb_rblocks, nsbp->sb_rextsize);
+		nsbp->sb_rextents = nsbp->sb_rblocks;
+		do_div(nsbp->sb_rextents, nsbp->sb_rextsize);
 		nsbp->sb_rextslog = xfs_highbit32(nsbp->sb_rextents);
 		nrsumlevels = nmp->m_rsumlevels = nsbp->sb_rextslog + 1;
 		nrsumsize =