Fix Wi-Fi level out of range crash

- If the Wi-Fi level is less than the minimum level, use the minimum
  level instead.

- If the Wi-Fi level is greater than the maximum level, use the
  maximum level instead.

Bug: 230457323
Test: manual test
make RunSettingsLibRoboTests ROBOTEST_FILTER=WifiUtilsTest

Change-Id: I7ec748ac200a7930ea08604ecf9cece6fcbfbb86