Bluetooth: qca: Update firmware-name to support board specific nvm

Different connectivity boards may be attached to the same platform. For
example, QCA6698-based boards can support either a two-antenna or
three-antenna solution, both of which work on the sa8775p-ride platform.
Due to differences in connectivity boards and variations in RF
performance from different foundries, different NVM configurations are
used based on the board ID.

Therefore, in the firmware-name property, if the NVM file has an
extension, the NVM file will be used. Otherwise, the system will first
try the .bNN (board ID) file, and if that fails, it will fall back to
the .bin file.

Possible configurations:
firmware-name = "QCA6698/hpnv21";
firmware-name = "QCA6698/hpnv21.bin";

Signed-off-by: Cheng Jiang <quic_chejiang@quicinc.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>