MAINTAINERS: update bq27xxx driver

Update reviewers for bq27xxx, so that Pali and Andrew
are reviewers with status and maintainer inherited from
the power supply subsystem entry.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Andrew F. Davis <afd@ti.com>