net: wifi: shell: enhance consistency in `cmd_wifi_dpp_ap_auth_init`

The `cmd_wifi_dpp_ap_auth_init` function was added but is not yet
aligned with others.
This update enhances consistency with the following changes:
- Unified the order of declaration for `opt`, `opt_index`,
  `state`, and `long_options`.
- Wrapped lines in the `long_options` declaration to prevent them
  from extending too far to the right.
- Applied `struct option` as `static const`
- Unified the wrapping of `getopt_long` calls, regardless of
  the length of the `options` string.
- Using `getopt_state` to access `optarg` and also `optopt` offers
  a better alternative to direct global access.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>