tmpfs: Overhaul option handling on remount

On remount, we must accept all the same options as on initial mount.
For parameters which we're unable to modify on the fly, fail only if
the new value is different from the existing one.

PR: 295096
MFC after: 1 week
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D57044

(cherry picked from commit 1cfc208a07b64a64377a4f8fe51c28f588a929cf)