mailmap: Fix text encoding for Niklas Söderlund

There are commits that mess up the encoding of 'ö' in Söderlund, add a
correct entry to .mailmap.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20211014212906.2331293-1-niklas.soderlund+renesas@ragnatech.seSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

.mailmap

@@ -276,6 +276,7 @@ Nicolas Pitre <nico@fluxnic.net> <nicolas.pitre@linaro.org>
 Nicolas Pitre <nico@fluxnic.net> <nico@linaro.org>
 Nicolas Saenz Julienne <nsaenz@kernel.org> <nsaenzjulienne@suse.de>
 Nicolas Saenz Julienne <nsaenz@kernel.org> <nsaenzjulienne@suse.com>
+Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
 Oleksij Rempel <linux@rempel-privat.de> <bug-track@fisher-privat.net>
 Oleksij Rempel <linux@rempel-privat.de> <external.Oleksij.Rempel@de.bosch.com>
 Oleksij Rempel <linux@rempel-privat.de> <fixed-term.Oleksij.Rempel@de.bosch.com>