broadcom/compiler: disable TMU pipelining if we fail to register allocate

broadcom/compiler: disable TMU pipelining if we fail to register allocate

TMU pipelining can severely reduce our capacity to emit TMU spills,
causing us to fail to compile a shader we may otherwise be able to
compile. This is because pipelining extends the liveness of TMU
sequences by posponing the thread switch and LDTMU until a result
is needed, and we can't emit TMU spills while in the middle of a
TMU sequence.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8825>