radv: allocate more space in the CS when emitting events

If the driver waits for CP DMA to be idle and emit an EOP event
we need more space.

This fixes a crash with Quake Champions.

Cc: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit 47a10ede)