drm/i915/vlv: remove wait for previous GFX clk disable request

drm/i915/vlv: remove wait for previous GFX clk disable request

Looks like it was introduced in:

commit 650ad970a39f8b6164fe8613edc150f585315289
Author: Imre Deak <[email protected]>
Date:   Fri Apr 18 16:35:02 2014 +0300

    drm/i915: vlv: factor out vlv_force_gfx_clock and check for pending force-of

but I'm not sure why.  It has caused problems for us in the past (see
85250ddff7a6 "drm/i915/chv: Remove Wait for a previous gfx force-off"
and 8d4eee9cd7a1 "drm/i915: vlv: increase timeout when forcing on the
GFX clock") and doesn't seem to be required, so let's just drop it.

References: https://bugs.freedesktop.org/show_bug.cgi?id=89611
Signed-off-by: Jesse Barnes <[email protected]>
Tested-by: Darren Hart <[email protected]>
Reviewed-by: Deepak S <[email protected]>
Cc: [email protected] # c9c52e24194a: drm/i915/chv: Remove Wait ...
Cc: [email protected]
Signed-off-by: Jani Nikula <[email protected]>