wlcore/wl12xx: remove deprecated FW version check

We don't distinguish between STA and AP firmwares anymore, so the
firmware version checking and quirks setting in wl12xx isn't needed
anymore.

Remove implementation of .identify_fw in wl12xx and deprecated
definitions.  Don't remove the op entirely from wlcore, because it may
be needed for more fine-grained checking later.

Signed-off-by: Luciano Coelho <coelho@ti.com>