power: supply: bq27xxx_battery: don't update poll_interval param if same

To avoid canceling the delayed workqueue needlessly, and scheduling an
immediate polling. Check if the new poll_interval value is different
than the previous setting.

Cc: Tony Lindgren <tony@atomide.com>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
Signed-off-by: Sebastian Reichel <sre@kernel.org>