wlcore/wl12xx/wl18xx: check min FW version

Refuse to boot if the FW version is too old. The minimum version is set
per chip, with the option of setting it per PG in the future.

When boot fails because of an old FW, display a helpful message.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>