Bluetooth: hci_qca: mark OF related data as maybe unused

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

  drivers/bluetooth/hci_qca.c:1869:37: error: ‘qca_soc_data_wcn6750’
  defined but not used [-Werror=unused-const-variable=]
  drivers/bluetooth/hci_qca.c:1853:37: error: ‘qca_soc_data_wcn3998’
  defined but not used [-Werror=unused-const-variable=]
  drivers/bluetooth/hci_qca.c:1841:37: error: ‘qca_soc_data_wcn3991’
  defined but not used [-Werror=unused-const-variable=]
  drivers/bluetooth/hci_qca.c:1830:37: error: ‘qca_soc_data_wcn3990’
  defined but not used [-Werror=unused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/hci_qca.c

@@ -1827,7 +1827,7 @@ static const struct hci_uart_proto qca_proto = {
 	.dequeue	= qca_dequeue,
 };
 
-static const struct qca_device_data qca_soc_data_wcn3990 = {
+static const struct qca_device_data qca_soc_data_wcn3990 __maybe_unused = {
 	.soc_type = QCA_WCN3990,
 	.vregs = (struct qca_vreg []) {
 		{ "vddio", 15000  },
@@ -1838,7 +1838,7 @@ static const struct qca_device_data qca_soc_data_wcn3990 = {
 	.num_vregs = 4,
 };
 
-static const struct qca_device_data qca_soc_data_wcn3991 = {
+static const struct qca_device_data qca_soc_data_wcn3991 __maybe_unused = {
 	.soc_type = QCA_WCN3991,
 	.vregs = (struct qca_vreg []) {
 		{ "vddio", 15000  },
@@ -1850,7 +1850,7 @@ static const struct qca_device_data qca_soc_data_wcn3991 = {
 	.capabilities = QCA_CAP_WIDEBAND_SPEECH | QCA_CAP_VALID_LE_STATES,
 };
 
-static const struct qca_device_data qca_soc_data_wcn3998 = {
+static const struct qca_device_data qca_soc_data_wcn3998 __maybe_unused = {
 	.soc_type = QCA_WCN3998,
 	.vregs = (struct qca_vreg []) {
 		{ "vddio", 10000  },
@@ -1861,12 +1861,12 @@ static const struct qca_device_data qca_soc_data_wcn3998 = {
 	.num_vregs = 4,
 };
 
-static const struct qca_device_data qca_soc_data_qca6390 = {
+static const struct qca_device_data qca_soc_data_qca6390 __maybe_unused = {
 	.soc_type = QCA_QCA6390,
 	.num_vregs = 0,
 };
 
-static const struct qca_device_data qca_soc_data_wcn6750 = {
+static const struct qca_device_data qca_soc_data_wcn6750 __maybe_unused = {
 	.soc_type = QCA_WCN6750,
 	.vregs = (struct qca_vreg []) {
 		{ "vddio", 5000 },