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>