MAINTAINERS: Change in maintainer for AMD NTB

I would like to take maintainership for AMD NTB

Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Acked-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>