tmpfs - Fix arbitrary maximum file size limitation

tmpfs - Fix arbitrary maximum file size limitation

* tmpfs's maxfilesize was limited to the original tmpfs mount
  storage limit, prior to argument overrides.  In addition,
  the -f argument override would not increase the maxfilesize
  limit beyond the original storage limit anyway.

* Remove this limit calculation entirely.  Instead the limit
  is based on the storage limit which can be optioned at mount
  time.

* Fixes expectations when tmpfs is used to hold just a few (or
  even just one) file.

Reported-by: kerma