drm/i915: Turn off hsync and vsync on ADPA when disabling crt

According to PRM we need to disable hsync and vsync even though ADPA is
disabled. The previous code did infact do the opposite so we fix it.
Signed-off-by: NPatrik Jakobsson <patrik.r.jakobsson@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56359Tested-by: Nmax <manikulin@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_crt.c

@@ -88,7 +88,7 @@ static void intel_disable_crt(struct intel_encoder *encoder)
 	u32 temp;
 
 	temp = I915_READ(crt->adpa_reg);
-	temp &= ~(ADPA_HSYNC_CNTL_DISABLE | ADPA_VSYNC_CNTL_DISABLE);
+	temp |= ADPA_HSYNC_CNTL_DISABLE | ADPA_VSYNC_CNTL_DISABLE;
 	temp &= ~ADPA_DAC_ENABLE;
 	I915_WRITE(crt->adpa_reg, temp);
 }