fs/ext4: fix partition size get truncated in calculation

It may cause file system corruption when do a write operation.
This issue only affects boards that use 32 bit lbaint_t.

Signed-off-by: Ma Haijun <mahaijuns@gmail.com>
diff --git a/fs/ext4/dev.c b/fs/ext4/dev.c
index 787e041..e0b513a 100644
--- a/fs/ext4/dev.c
+++ b/fs/ext4/dev.c
@@ -41,7 +41,7 @@
 	get_fs()->dev_desc = rbdd;
 	part_info = info;
 	part_offset = info->start;
-	get_fs()->total_sect = (info->size * info->blksz) >>
+	get_fs()->total_sect = ((uint64_t)info->size * info->blksz) >>
 		get_fs()->dev_desc->log2blksz;
 }