Bluetooth: hci_intel: Update firmware filename for Intel 9x60 and later

The format of Intel Bluetooth firmware for bootloader product is
ibt-<hw_variant>-<device_revision_id>.sfi and .ddc.

But for the 9x60 SKU, there are three variants of FW, which cannot be
differenticate just with hw_variant and device_revision_id.
So, to pick the appropriate FW file for 9x60 SKU, three fields,
hw_variant, hw_revision, and fw_revision, needs to be used rather than
hw_variant and device_revision_id.

Format will be like this:
ibt-<hw_variant>-<hw_revision>-<fw_revision>.sfi and .ddc

Signed-off-by: Tedd Ho-Jeong An <tedd.an@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>