nouveau: avoid double-emitting fence
nouveau: avoid double-emitting fence

The act of ensuring that there is space can cause a flush to happen,
which will emit the current screen fence. If that is the fence we're
trying to wait on, then it will have been emitted as a result of doing
the PUSH_SPACE. Don't attempt to emit it a second time.

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Fixes: 8053c9208f (nouveau: avoid emitting new fences unnecessarily)
Cc: 59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler