net: wifi: Pass ssid as const
net: wifi: Pass ssid as const

There shouldn't be any reason to be able to modify the passed in SSID,
and having this non-const gives application warnings if passing a
constant string.

Signed-off-by: Ole Morten Haaland <6c61c2285efdd6b0c1458ddf90ef54bfb29eaf67@icsys.no>

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