Inform p2p framework about the channel change event

Added a callback function to indicate that the p2p
operating frequency has been changed.

Bug: 202758240
Test: vts test
Test: Manually triggered channel switch through hostapd command
    and verified the new frequency in logs.
Change-Id: I5814a108c77478cf96bc88f2d8fd8193bd8168be
3 files changed