Bluetooth: btmrvl_sdio: mark OF related data as maybe unused

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

  drivers/bluetooth/btmrvl_sdio.c:43:34: error:
  ‘btmrvl_sdio_of_match_table’ 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/btmrvl_sdio.c

@@ -40,7 +40,7 @@ static struct memory_type_mapping mem_type_mapping_tbl[] = {
 	{"EXTLAST", NULL, 0, 0xFE},
 };
 
-static const struct of_device_id btmrvl_sdio_of_match_table[] = {
+static const struct of_device_id btmrvl_sdio_of_match_table[] __maybe_unused = {
 	{ .compatible = "marvell,sd8897-bt" },
 	{ .compatible = "marvell,sd8997-bt" },
 	{ }