drm/i915: Rebalance runtime pm vs forcewake

drm/i915: Rebalance runtime pm vs forcewake

Calling intel_runtime_pm_put() is illegal from a soft-irq context, so
revert the crude hack

commit aa0b3b5bb8768c1a6a6788869d9c7015eae7e80c
Author: Paulo Zanoni <[email protected]>
Date:   Tue Apr 1 14:55:07 2014 -0300

    drm/i915: don't schedule force_wake_timer at gen6_read

and apply the single line corrective instead.

v2: assert forcewake is off after the forcewake_reset (Paulo)

References: https://bugs.freedesktop.org/show_bug.cgi?id=80913
Cc: Paulo Zanoni <[email protected]>
Cc: Daniel Vetter <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Signed-off-by: Mika Kuoppala <[email protected]>
Reviewed-by: Deepak S <[email protected]> (v1)
Signed-off-by: Daniel Vetter <[email protected]>