mailmap: update email for Iskren Chernev

I'm sunsetting my gmail account and moving to personal domain.

Link: https://lkml.kernel.org/r/20221124114356.2187901-1-me@iskren.infoSigned-off-by: Iskren Chernev <me@iskren.info>
Acked-by: Iskren Chernev <iskren.chernev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

.mailmap

@@ -227,6 +227,7 @@ Juha Yrjola <at solidboot.com>
 Juha Yrjola <juha.yrjola@nokia.com>
 Juha Yrjola <juha.yrjola@solidboot.com>
 Julien Thierry <julien.thierry.kdev@gmail.com> <julien.thierry@arm.com>
+Iskren Chernev <me@iskren.info> <iskren.chernev@gmail.com>
 Kalle Valo <kvalo@kernel.org> <kvalo@codeaurora.org>
 Kalyan Thota <quic_kalyant@quicinc.com> <kalyan_t@codeaurora.org>
 Kay Sievers <kay.sievers@vrfy.org>