Documentation: filesystems: xfs: update pseudocode and typo fixes

According to the implementation of xfs_trans_roll(), it calls
xfs_trans_reserve(), which reserves not only log space, but also
free disk blocks. In short, the "transaction stuff". So change
xfs_log_reserve() to xfs_trans_reserve().

Besides, fix several typo issues.

Signed-off-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220823013653.203469-1-zhaomzhao@126.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>