[struct mount] Outdated locking documentation for mnt_uppers

[Konstantin Belousov]

On Wed, Apr 07, 2021 at 09:50:18PM +0200, Alexander Lochmann wrote:
> Hi folks,
> 
> I came accross the locking documentation for struct mount.
> According to the definition [1], mnt_uppers should be accessed using the
> global mountlist_mtx.
> However, the code uses the MNT_ILOCK macro, which uses the mnt_mtx.
> Is the locking documentation still valid?
> Shouldn't it be updated?

Thank you for the report, done in 5af1131de7fc.