MAINTAINERS: change the maintainer of fam15h_power driver

Andreas Herrmann won't take the maintainer of fam15h_power driver. I
will take it and appreciate him for the great contributions on this
driver.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Acked-by: Andreas Herrmann <herrmann.der.user@googlemail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
[groeck: Fixed typo in CREDITS]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>