[rdk-b][mt7986][wifi-hal][Refactor get ap enable and get channel bandwidth functions]

[Description]
Refactor these two functions to stop annoying error message.
Wi-Fi agent call them every 5 seconds.
If the radio is not set up, the command would ouput command fail message to stderr. Thus, add a check and move error message to /dev/null in two functions.
In getApEnable, we only consider stdout output.

[Release-log]
N/A

1 file changed