Bluetooth: btnxpuart: Add support for AW693 chipset

This adds support for NXP AW693 chipset in btnxpuart driver
by adding FW name and bootloader signature. Based on the
loader version bits 7:6 of the bootloader signature, the
driver can choose between selecting secure and non-secure
FW files.

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>