Bluetooth: btintel: Fix compiler warning for multi_v7_defconfig config

Fix the following compiler warning reported for ARCH=arm
multi_v7_defconfig.

In file included from drivers/bluetooth/hci_ldisc.c:34:
drivers/bluetooth/btintel.h:373:13: warning: 'btintel_hw_error' defined
but not used [-Wunused-function]
  373 | static void btintel_hw_error(struct hci_dev *hdev, u8 code)
      |             ^~~~~~~~~~~~~~~~

cc: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 67d4dbac ("Bluetooth: btintel: Export few static functions")
Signed-off-by: Kiran K <kiran.k@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>