Bluetooth: btnxpuart: Add uevents for FW dump and FW download complete

Bluetooth: btnxpuart: Add uevents for FW dump and FW download complete

This adds uevents which will be generated whenever FW dump is triggered,
FW dump is complete and FW (re)download is done.

This feature is needed for IW612 chipset, which is a tri-radio chipset,
where WLAN runs on CPU1 and BT and Zigbee runs on CPU2.

Currently, whenever BT FW crashes, and FW dump is in progress, there is
no way for 15.4 application to know that CPU2 is in bad state, and when
it will be recovered.

With the help of these uevents and udev rules, the 15.4 app, or any
userspace application can be alerted whenever CPU2 goes in bad state and
recoveres after BTNXPUART reloads the firmware.

[  334.255154] Bluetooth: hci0: ==== Start FW dump ===
[  334.261003] Bluetooth: hci0: ==== Send uevent: BTNXPUART_DEV=serial0-0:BTNXPUART_STATE=FW_DUMP_ACTIVE ===
[  351.486048] Bluetooth: hci0: ==== FW dump complete ===
[  351.491356] Bluetooth: hci0: ==== Send uevent: BTNXPUART_DEV=serial0-0:BTNXPUART_STATE=FW_DUMP_DONE ===
[  352.028974] Bluetooth: hci0: ChipID: 7601, Version: 0
[  352.034490] Bluetooth: hci0: Request Firmware: nxp/uartspi_n61x_v1.bin.se
[  353.979977] Bluetooth: hci0: FW Download Complete: 417064 bytes
[  355.197222] Bluetooth: hci0: ==== Send uevent: BTNXPUART_DEV=serial0-0:BTNXPUART_STATE=FW_READY ===

Tested this change by creating a simple udev rule to store the
BTNXPUART_STATE value in a ~/<BTNXPUART_DEV>/state file, and running
15.4 traffic.

The 15.4 packets were sent over SPI only when BTNXPUART_STATE was
FW_READY.

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Tested-by: Jean-Yves Salaün <jean-yves.salaun@nxp.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>