MAINTAINERS: update email address for Naoya Horiguchi

My email address has changed due to system upgrade, so please update it
in MAINTAINERS list.  My old address (n-horiguchi@ah.jp.nec.com) will be
still active for a few months.

Note that my email system has some encoding issue and can't send patches
in raw format via git-send-email.  So patches from me will be delivered
via my free address (nao.horiguchi@gmail.com) or GitHub.
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1589874488-9247-1-git-send-email-naoya.horiguchi@nec.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -7829,7 +7829,7 @@ T:	git git://linuxtv.org/media_tree.git
 F:	drivers/media/platform/sti/hva
 
 HWPOISON MEMORY FAILURE HANDLING
-M:	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
+M:	Naoya Horiguchi <naoya.horiguchi@nec.com>
 L:	linux-mm@kvack.org
 S:	Maintained
 F:	mm/hwpoison-inject.c