net: wwan: t7xx: Add debug ports

net: wwan: t7xx: Add debug ports

Add support for userspace to enable/disable the debug ports(ADB,MIPC).
 - ADB port: /dev/wwan0adb0
 - MIPC port: /dev/wwan0mipc0

Application can use ADB (Android Debug Bridge) port to implement
functions (shell, pull, push ...) by ADB protocol commands.
E.g., ADB commands:
 - A_OPEN: OPEN(local-id, 0, "destination")
 - A_WRTE: WRITE(local-id, remote-id, "data")
 - A_OKEY: READY(local-id, remote-id, "")
 - A_CLSE: CLOSE(local-id, remote-id, "")

Link: https://android.googlesource.com/platform/packages/modules/adb/+/refs/heads/main/README.md
Application can use MIPC (Modem Information Process Center) port
to debug antenna tuner or noise profiling through this MTK modem
diagnostic interface.

By default, debug ports are not exposed, so using the command
to enable or disable debug ports.

Enable debug ports:
 - enable: 'echo 1 > /sys/bus/pci/devices/${bdf}/t7xx_debug_ports

Disable debug ports:
 - disable: 'echo 0 > /sys/bus/pci/devices/${bdf}/t7xx_debug_ports

Signed-off-by: Jinjian Song <jinjian.song@fibocom.com>
Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>