ext4: fix miscellaneous big endian warnings

None of these result in any bug, but they makes sparse complain.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/xattr.c

@@ -122,17 +122,18 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
 				    struct ext4_xattr_header *hdr)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	__u32 csum, old;
+	__u32 csum;
+	__le32 save_csum;
+	__le64 dsk_block_nr = cpu_to_le64(block_nr);
 
-	old = hdr->h_checksum;
+	save_csum = hdr->h_checksum;
 	hdr->h_checksum = 0;
-	block_nr = cpu_to_le64(block_nr);
-	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
-			   sizeof(block_nr));
+	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&dsk_block_nr,
+			   sizeof(dsk_block_nr));
 	csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
 			   EXT4_BLOCK_SIZE(inode->i_sb));
 
-	hdr->h_checksum = old;
+	hdr->h_checksum = save_csum;
 	return cpu_to_le32(csum);
 }