[FIX] hw_drivers: Fix get_wifi_essid helper
[FIX] hw_drivers: Fix get_wifi_essid helper

The `get_wifi_essid` function was moved to the helpers file, but the
`self` argument was not removed from the function's signature.

closes odoo/odoo#36710

Signed-off-by: Quentin Lejeune (qle) <5d1c09880ce30fdcf63039932dac0c183ef0bdc7@odoo.com>

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