linux-phytec-fsl

MAINTAINERS: update power-supply git-tree

When I took over the power-supply tree, its git tree was
hosted on git.infradead.org. Since a few kernel releases I
also maintain a copy of the repository on git.kernel.org,
that is prefered by Linus, so let's switch over officially.

Signed-off-By: Sebastian Reichel <sre@kernel.org>