P2P: Allow P2P CSA from 5 GHz to 2.4 GHz band

P2P: Allow P2P CSA from 5 GHz to 2.4 GHz band

IEEE Std 802.11-2020, 11.8.8 (Selecting and advertising a new channel)
doesn't restrict switching to a channel which is not in the same band as
the current band. But at the same time, there are some issues in
switching between the 2.4/5 GHz bands and the 6 GHz band. So limit the
check to consider the critical use case of switching from a 5 GHz channel
to a 2.4 GHz channel.

Signed-off-by: Sunil Ravi <sunilravi@google.com>