ASoC: wm_hubs: Convert headphone driver to output driver widget

Mostly for neatness, though it may help with sequencing in some
situations.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/wm_hubs.c

@@ -670,8 +670,7 @@ SND_SOC_DAPM_PGA("Right Output PGA", WM8993_POWER_MANAGEMENT_3, 6, 0, NULL, 0),
 
 SND_SOC_DAPM_SUPPLY("Headphone Supply", SND_SOC_NOPM, 0, 0, hp_supply_event, 
 		    SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_PRE_PMD),
-SND_SOC_DAPM_PGA_E("Headphone PGA", SND_SOC_NOPM, 0, 0,
-		   NULL, 0,
+SND_SOC_DAPM_OUT_DRV_E("Headphone PGA", SND_SOC_NOPM, 0, 0, NULL, 0,
 		       hp_event, SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD),
 
 SND_SOC_DAPM_MIXER("Earpiece Mixer", SND_SOC_NOPM, 0, 0,