scripts/netifd-wireless.sh: properly fix WPA3 Enterprise support

scripts/netifd-wireless.sh: properly fix WPA3 Enterprise support

Support the following values for the different WPA3 Enterprise modes:

- wpa3-mixed: WPA3 Enterprise transitional mode
	This supports EAP with both SHA1 and SHA-256, with optional MFP
- wpa3: WPA3 Enterprise only mode
	This supports only SHA256 with mandatory MFP
- wpa3-192: WPA3 Enterprise with mandatory 192 bit support
	This uses only GCMP-256 ciphers

Disable 192 bit support and GCMP-256 ciphers for the regular "wpa3" mode.
It seems that even leaving in optional 192 bit support breaks auth on some
clients, including iOS devices.

Signed-off-by: Felix Fietkau <nbd@nbd.name>