fix disconnect print fail log

[GaofengZhangNXP]

WIFI_REASON_DISCONN_UNSPECIFIED is 1, when disconnect reason is 0, wpas_to_wifi_mgmt_disconn_status return the WIFI_REASON_DISCONN_UNSPECIFIED and print error log "Disconnection request failed (1)"

[github-actions]

Hello @GaofengZhangNXP, and thank you very much for your first pull request to the Zephyr project!
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[gannicus-gj]

Hi @krish2718 , @jukkar
could you pls take time to review this change, thanks