MAINTAINERS: add Andrew and Baoquan as kexec maintainers

MAINTAINERS: add Andrew and Baoquan as kexec maintainers

Add Andrew as kexec/kdump maintainer because he has been helping review
and merge ready kexec/kdump patches.

And I would like to nominate myself as kexec maintainer because I always
try to review generic kexec codes.

Link: https://lkml.kernel.org/r/20250328104402.16826-1-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Acked-by: Simon Horman <horms@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>