drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register()

By using the out-of-line intel_wait_for_register() not only do we can
efficiency from using the hybrid wait_for() contained within, but we
avoid code bloat from the numerous inlined loops, in total (all patches):

   text    data     bss     dec     hex filename
1078551    4557     416 1083524  108884 drivers/gpu/drm/i915/i915.ko
1070775    4557     416 1075748  106a24 drivers/gpu/drm/i915/i915.ko

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467297225-21379-29-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -856,7 +856,11 @@ static void skl_ddi_pll_enable(struct drm_i915_private *dev_priv,
 	I915_WRITE(regs[pll->id].ctl,
 		   I915_READ(regs[pll->id].ctl) | LCPLL_PLL_ENABLE);
 
-	if (wait_for(I915_READ(DPLL_STATUS) & DPLL_LOCK(pll->id), 5))
+	if (intel_wait_for_register(dev_priv,
+				    DPLL_STATUS,
+				    DPLL_LOCK(pll->id),
+				    DPLL_LOCK(pll->id),
+				    5))
 		DRM_ERROR("DPLL %d not locked\n", pll->id);
 }