drm/omap: check return value from soc_device_match

soc_device_match() can return NULL, so add a check and fail if
soc_device_match() fails.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180502091159.7071-2-tomi.valkeinen@ti.com
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/omapdrm/dss/hdmi4_core.c

@@ -922,8 +922,13 @@ int hdmi4_core_init(struct platform_device *pdev, struct hdmi_core_data *core)
 {
 	const struct hdmi4_features *features;
 	struct resource *res;
+	const struct soc_device_attribute *soc;
 
-	features = soc_device_match(hdmi4_soc_devices)->data;
+	soc = soc_device_match(hdmi4_soc_devices);
+	if (!soc)
+		return -ENODEV;
+
+	features = soc->data;
 	core->cts_swmode = features->cts_swmode;
 	core->audio_use_mclk = features->audio_use_mclk;