radv: fix re-emitting streamout descriptors for NGG streamout

radv: fix re-emitting streamout descriptors for NGG streamout

In a scenario like:
CmdBindTransformFeedbackBuffers()
BeginTransformFeedback()
CmdDraw() --> streamout descriptors emitted
EndTransformFeedback() --> streamout descriptors emitted as 0 (disabled)
CmdDraw()
BeginTransformFeedback()
CmdDraw() --> streamout descriptor not re-emitted
EndTransformFeedback()

Fix this by re-emitting streamout descriptors when streamout is
enabled/disabled because a buffer size of 0 acts like a disable bit.

This fixes dEQP-VK.transform_feedback.simple.backward_dependency_indirect*
on NAVI31.

Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25583>