MAINTAINERS: exfat: update my email address

My email address in exfat entry will be not available in a few days.
Update it to my own kernel.org address.

Link: https://lkml.kernel.org/r/20210825044833.16806-1-namjae.jeon@samsung.com


Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>