Fix a signed vs unsigned and a void * pointer arithmetic warning.
This cleanup is also in e2fsprogs commit 
aec460db9a93 ("e2fsck: clean
up two gcc -Wall warnings in recovery.c").
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
        if (!jbd2_journal_has_csum_v2or3(j))
                return 1;
 
-       tail = (struct jbd2_journal_block_tail *)(buf + j->j_blocksize -
-                       sizeof(struct jbd2_journal_block_tail));
+       tail = (struct jbd2_journal_block_tail *)((char *)buf +
+               j->j_blocksize - sizeof(struct jbd2_journal_block_tail));
        provided = tail->t_checksum;
        tail->t_checksum = 0;
        calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
 {
        jbd2_journal_revoke_header_t *header;
        int offset, max;
-       int csum_size = 0;
+       unsigned csum_size = 0;
        __u32 rcount;
        int record_len = 4;