rt946x: polish charger log format
rt946x: polish charger log format

Prefix logs with RT946X and add some minor information

TEST=make buildall
BUG=None
BRANCH=kukui

Change-Id: I10992c1d8fbde97eb70bf29c655ea124ce80891f
Signed-off-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1980106
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec