lib/littlefs: Guard lfs2_mlist_isopen with LFS2_NO_ASSERT.
lib/littlefs: Guard lfs2_mlist_isopen with LFS2_NO_ASSERT.

To prevent warnings about this function being unused when assertions are
disabled.

Signed-off-by: Damien George <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@micropython.org>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython