st/nine: Add dummy ff shader state

st/nine: Add dummy ff shader state

Some states only affect the ff shader,
not its constants.
Currently we don't check anything and
always recompute the ff shader key.

However we do check for NINE_STATE_FF_OTHER
and if set we reupload some constants.

Thus for those states which had NINE_STATE_FF_OTHER
set but didn't need it,
replace by a dummy ff shader state (which is
easier to understand for an external reader than
just setting 0 and more future proof).

Signed-off-by: Axel Davy <davyaxel0@gmail.com>