docs(maintainers): update nxp layerscape maintainers

Added myself to be NXP common code and ls1028a, ls1043a platforms
maintainer.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: Iadffc5600e9bb2e94b1d545b8dd1a819358cabcb
1 file changed