Bluetooth: qca: Expand firmware-name to load specific rampatch

The firmware-name property has been expanded to specify the names of NVM
and rampatch firmware for certain chips, such as the QCA6698 Bluetooth
chip. Although it shares the same IP core as the WCN6855, the QCA6698
has different RF components and RAM sizes, necessitating new firmware
files. This change allows for the configuration of NVM and rampatch in
DT.

Possible configurations:
firmware-name = QCA6698/hpnv21.bin, QCA6698/hpbtfw21.tlv;
firmware-name = QCA6698/hpnv21, QCA6698/hpbtfw21.tlv;

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