udf: Fix inode_getblk() return value

udf: Fix inode_getblk() return value

Smatch noticed that inode_getblk() can return 1 on successful mapping of
a block instead of expected 0 after commit b405c1e58b73 ("udf: refactor
udf_next_aext() to handle error"). This could confuse some of the
callers and lead to strange failures (although the one reported by
Smatch in udf_mkdir() is impossible to trigger in practice). Fix the
return value of inode_getblk().

Link: https://lore.kernel.org/all/cb514af7-bbe0-435b-934f-dd1d7a16d2cd@stanley.mountain
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Fixes: b405c1e58b73 ("udf: refactor udf_next_aext() to handle error")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>