f2fs: remove unreachable lazytime mount option parsing

The lazytime/nolazytime options are now handled in the VFS, and are
never seen in filesystem parsers, so remove handling of these
options from f2fs.

Note: when lazytime support was added in 6d94c74a it made
lazytime the default in default_options() - as a result, lazytime
cannot be disabled (because Opt_nolazytime is never seen in f2fs
parsing).

If lazytime is desired to be configurable, and default off is OK,
default_options() could be updated to stop setting it by default
and allow mount option control.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>