drm/i915/power: use intel_de_wait_custom() instead of wait_for_us()

Prefer the register read specific wait function over i915 wait_for_us().

Reviewed-by: Gustavo Sousa <[e-mail]>
Link: https://lore.kernel.org/r/154[e-mail]
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/i915/display/intel_display_power.c

···
 			      bool switch_to_fclk, bool allow_power_down)
 {
 	u32 val;
+	int ret;
 
 	assert_can_disable_lcpll(display);
 
···
 		val |= LCPLL_CD_SOURCE_FCLK;
 		intel_de_write(display, LCPLL_CTL, val);
 
-		if (wait_for_us(intel_de_read(display, LCPLL_CTL) &
-				LCPLL_CD_SOURCE_FCLK_DONE, 1))
+		ret = intel_de_wait_custom(display, LCPLL_CTL,
+					   LCPLL_CD_SOURCE_FCLK_DONE, LCPLL_CD_SOURCE_FCLK_DONE,
+					   1, 0, NULL);
+		if (ret)
 			drm_err(display->drm, "Switching to FCLK failed\n");
 
 		val = intel_de_read(display, LCPLL_CTL);
···
 {
 	struct drm_i915_private __maybe_unused *dev_priv = to_i915(display->drm);
 	u32 val;
+	int ret;
 
 	val = intel_de_read(display, LCPLL_CTL);
 
···
 	if (val & LCPLL_CD_SOURCE_FCLK) {
 		intel_de_rmw(display, LCPLL_CTL, LCPLL_CD_SOURCE_FCLK, 0);
 
-		if (wait_for_us((intel_de_read(display, LCPLL_CTL) &
-				 LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
+		ret = intel_de_wait_custom(display, LCPLL_CTL,
+					   LCPLL_CD_SOURCE_FCLK_DONE, 0,
+					   1, 0, NULL);
+		if (ret)
 			drm_err(display->drm,
 				"Switching back to LCPLL failed\n");
 	}