Bluetooth: NXP: Add protocol support for NXP Bluetooth chipsets

This adds a driver based on serdev driver for the NXP BT serial protocol
based on running H:4, which can enable the built-in Bluetooth device
inside an NXP BT chip.

This driver has Power Save feature that will put the chip into sleep state
whenever there is no activity for 2000ms, and will be woken up when any
activity is to be initiated over UART.

This driver enables the power save feature by default by sending the vendor
specific commands to the chip during setup.

During setup, the driver checks if a FW is already running on the chip
by waiting for the bootloader signature, and downloads device specific FW
file into the chip over UART if bootloader signature is received..

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>