drm/msm: reset devfreq freq_table/max_state before devfreq_add_device

These never get set back to 0 when probing fails, so an attempt to probe
again results in broken behavior. Fix the problem by setting thse to zero
before they are used.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Rob Clark <robdclark@chromium.org>