radv: bitcast 16-bit outputs to integers

16-bit outputs are stored as 16-bit floats in the outputs array, so they
have to be bitcast.

Fixes: b722b29f ('radv: add support for 16bit input/output')
Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
(cherry picked from commit 64065aa5)