iwm - Track firmware state better, and improve handling in iwm_newstate().

• This avoids firmware resets in all the cases in iwm_newstate(). Instead

iwm_bring_down_firmware() is called, which tears down all the STA
connection state, according to the sc->sc_firmware_state value.

• Improve the behaviour of the LED blinking a bit, so it only blinks when

there really is a wireless scan going on.

• Print the newstate arg in debug output of iwm_newstate(), to help in

debugging.

This is inspired by the firmware state maintaining change in OpenBSD's iwm,
by stsp@openbsd.org (OpenBSD Git 0ddb056fb7370664b1d4b84392697cb17d1a414a).

Submitted by: Augustin Cavalier <waddlesplash@gmail.com> (Haiku)
Obtained from: DragonFlyBSD (8a41b10ac639d0609878696808387a6799d39b57)