MAINTAINERS: Make Yazen Ghannam maintainer for EDAC-AMD64

Also, include the mce_amd* files under this section.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210525194834.2710362-1-Yazen.Ghannam@amd.com