thermal: gov_power_allocator: Update total_weight on bind and cdev updates

params->total_weight is not initialized during bind and not updated when
the bound cdev changes. The cooling device weight will not be used due
to the uninitialized total_weight, until an update via sysfs is
triggered.

The bound cdevs are updated during thermal zone registration, where each
cooling device will be bound to the thermal zone one by one, but
power_allocator_bind() can be called without an additional cdev update
when manually changing the policy of a thermal zone via sysfs.

Add a new function to handle weight update logic, including updating
total_weight, and call it when bind, weight changes, and cdev updates to
ensure total_weight is always correct.

Fixes: a3cd6db4 ("thermal: gov_power_allocator: Support new update callback of weights")
Signed-off-by: Yu-Che Cheng <giver@chromium.org>
Link: https://patch.msgid.link/20250222-fix-power-allocator-weight-v2-1-a94de86b685a@chromium.org


[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>