drm/msm/a6xx: Fix speed-bin detection vs probe-defer

drm/msm/a6xx: Fix speed-bin detection vs probe-defer

If we get an error (other than -ENOENT) we need to propagate that up the
stack.  Otherwise if the nvmem driver hasn't probed yet, we'll end up
end up claiming that we support all the OPPs which is not likely to be
true (and on some generations impossible to be true, ie. if there are
conflicting OPPs).

v2: Update commit msg, gc unused label, etc
v3: Add previously missing \n's

Fixes: fe7952c629da ("drm/msm: Add speed-bin support to a618 gpu")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/511690/
Link: https://lore.kernel.org/r/20221115154637.1613968-1-robdclark@gmail.com