ASoC: es7134: mark OF related data as maybe unused

The driver can be compile tested with !CONFIG_OF making certain data
unused:

  sound/soc/codecs/es7134.c:264:33: warning: ‘es7154_chip’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201125164452.89239-34-krzk@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/es7134.c

@@ -183,7 +183,7 @@ static const struct snd_soc_dapm_route es7134_extra_routes[] = {
 	{ "Playback", NULL, "VDD", }
 };
 
-static const struct es7134_chip es7134_chip = {
+static const struct es7134_chip es7134_chip __maybe_unused = {
 	.dai_drv = &es7134_dai,
 	.modes = es7134_modes,
 	.mode_num = ARRAY_SIZE(es7134_modes),
@@ -261,7 +261,7 @@ static const struct snd_soc_dapm_route es7154_extra_routes[] = {
 	{ "Playback", NULL, "PVDD", }
 };
 
-static const struct es7134_chip es7154_chip = {
+static const struct es7134_chip es7154_chip __maybe_unused = {
 	.dai_drv = &es7154_dai,
 	.modes = es7154_modes,
 	.mode_num = ARRAY_SIZE(es7154_modes),