drm/i915: GMBUS don't need no forcewake

GMBUS is part of the display engine, and thus has no need for
forcewake. Let's not bother trying to grab it then.

I don't recall if the display engine suffers from system hangs
due to multiple accesses to the same "cacheline" in mmio space.
I hope not since we're no longer protected by the uncore lock
since commit 4e6c2d58ba86 ("drm/i915: Take forcewake once for
the entire GMBUS transaction")

Cc: Chris Wilson <[e-mail]>
Cc: David Weinehall <[e-mail]>
Signed-off-by: Ville Syrjälä <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: Chris Wilson <[e-mail]>

drivers/gpu/drm/i915/intel_i2c.c

···
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = bus->dev_priv;
-	const unsigned int fw =
-		intel_uncore_forcewake_for_reg(dev_priv, GMBUS0,
-					       FW_REG_READ | FW_REG_WRITE);
 	int i = 0, inc, try = 0;
 	int ret = 0;
 
-	intel_uncore_forcewake_get(dev_priv, fw);
 retry:
 	I915_WRITE_FW(GMBUS0, bus->reg0);
 
···
 	ret = -EAGAIN;
 
 out:
-	intel_uncore_forcewake_put(dev_priv, fw);
 	return ret;
 }