MAINTAINERS: fix incorrect mail address of XFS maintainer

When I tried to send the patches to XFS Maintainers,
I got returned mail included delivery fail message for Dave's mail.
Maybe, Dave Chinner mail address is incorrect.
I try to fix it correctly.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

(cherry picked from commit db10bddc)