ext4: change token2str() to use ext4_param_specs

Change token2str() to use ext4_param_specs instead of tokens so that we
can get rid of tokens entirely.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Link: https://lore.kernel.org/r/20211027141857.33657-12-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>