MAINTAINERS: orphan BEFS

This old address bounces and Sergey doesn't answer at another email
address.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Sergey Kostyliov <rathamahata@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>