Added AP collection diagnosis function description

Added AP collection diagnosis function description

1)      The AC version starts from 5452, and supports obtaining AP diagnosis from the AC command line:

[office-probe]dis wlan ap name luyou diagnostic-information

Diagnostic information is being output to flash:/apdiag/apdiag_luyou.tar.gz

Saved successfully.

2)      After AC version 5455, Yunjian supports directly obtaining thin AP diagnosis from the cloud. Currently, it only supports obtaining a single AP and a single AP.

PS: WA6500a series AP expects E2488 to support Ac collection diagnosis function