MAINTAINERS: Add a maintainer entry for FRED

Add H. Peter Anvin and myself as FRED maintainers.

Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Link: https://lore.kernel.org/r/20240131080143.3259642-1-xin@zytor.com