mailmap: normalize name for Yoichi NAKAYAMA

Normalize name formatting and map older formats to the canonical one.

Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.mailmap

diff --git a/.mailmap b/.mailmap
index e3fab1d..29b4890 100644
--- a/.mailmap
+++ b/.mailmap
@@ -312,6 +312,7 @@
 YONETANI Tomokazu <y0n3t4n1@gmail.com> <y0netan1@dragonflybsd.org>
 YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
 Yi-Jyun Pan <pan93412@gmail.com>
+Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
 # the two anonymous contributors are different persons:
 anonymous <linux@horizon.com>
 anonymous <linux@horizon.net>