ASoC: hdmi-codec: use sizeof_field rather than declaring hcp

Use FIELD_SIZEOF rather than declaring and initializing hcp. Remove
unused variables. Cleans up clang warning:

warning: Value stored to 'hcp' during its initialization is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/codecs/hdmi-codec.c

@@ -303,11 +303,8 @@ enum {
 static int hdmi_eld_ctl_info(struct snd_kcontrol *kcontrol,
 			     struct snd_ctl_elem_info *uinfo)
 {
-	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
-	struct hdmi_codec_priv *hcp = snd_soc_component_get_drvdata(component);
-
 	uinfo->type = SNDRV_CTL_ELEM_TYPE_BYTES;
-	uinfo->count = sizeof(hcp->eld);
+	uinfo->count = FIELD_SIZEOF(struct hdmi_codec_priv, eld);
 
 	return 0;
 }