P2P: Include p2p_6ghz_disable in global configuration

P2P: Include p2p_6ghz_disable in global configuration

Previously, the configuration to disable the 6 GHz band remained local
to the P2P interface. With this there is a possibility of 6 GHz channels
being included in the channel list when the channel list needs to be
updated if the state changes on one of the interfaces.

Include the configuration to disable the 6 GHz band for P2P as a global
configuration value to prevent the inclusion of 6 GHz channels in the
channel list for P2P when the channel list needs to be updated during
the state change in one of the interfaces.

Signed-off-by: Sreeramya Soratkal <ssramya@codeaurora.org>