ARM: imx_v6_v7_defconfig: Select HDMI audio support

Select CONFIG_DRM_DW_HDMI_AHB_AUDIO so that we have HDMI audio
supported by default.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -223,6 +223,7 @@ CONFIG_SOC_CAMERA_OV2640=y
 CONFIG_IMX_IPUV3_CORE=y
 CONFIG_DRM=y
 CONFIG_DRM_PANEL_SIMPLE=y
+CONFIG_DRM_DW_HDMI_AHB_AUDIO=m
 CONFIG_DRM_IMX=y
 CONFIG_DRM_IMX_FB_HELPER=y
 CONFIG_DRM_IMX_PARALLEL_DISPLAY=y