LinuxKPI: 802.11: make lkpi_ic_set_channel() unconditional

For (*config)() based drivers not using chanctx we need to use
ic_set_channel() to switch channels. So far this was disabled
based on scanning flags (as swscan is one of the initial use cases
for this function). Now make it only dependent on (*config)()
for the moment to save us the work if (*config)() is not supported.

For iwlwifi (*config)() is a NOP so no functional changes there
but for other drivers such as rtw88 this will allow us to scan and
set the channel (which helps to receive on channels other than 1).

Sponsored by: The FreeBSD Foundation

(cherry picked from commit b2cf3c2125bf6f34cb01296e7eda93f73bc4b715)