thermal: gov_bang_bang: Relocate regulation logic description

Move the regulation logic description from the bang_bang_trip_crossed()
kerneldoc to the preamble.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/4987649.31r3eYUQgx@rjwysocki.net


[ rjw: Removed a trailing whitespace ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>