Bluetooth: hci_qca: Load customized NVM based on the device property

QCA BTSOC NVM is a customized firmware file and different vendors may
want to have different BTSOC configuration (e.g. Configure SCO over PCM
or I2S, Setting Tx power, etc.) via this file. This patch will allow
vendors to download different NVM firmware file by reading a device
property "firmware-name".

Signed-off-by: Rocky Liao <rjliao@codeaurora.org>
Tested-by: Harish Bandi <c-hbandi@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>