Fix miscellaneous gcc -Wall warnings

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/lib/ext2fs/bmap.c b/lib/ext2fs/bmap.c
index 24f05fd..5fe0986 100644
--- a/lib/ext2fs/bmap.c
+++ b/lib/ext2fs/bmap.c
@@ -158,7 +158,7 @@
 
 	if (inode->i_flags & EXT4_EXTENTS_FL) {
 		struct ext2fs_extent	extent;
-		int			offset;
+		unsigned int		offset;
 
 		if (bmap_flags & BMAP_SET) {
 			retval = EXT2_ET_EXTENT_NOT_SUPPORTED;