maintainers: allwinner: add missing link to github page

A proper link to Samuel's github page was missing. Add this to make
the link actually work.

Change-Id: I68b116935bf045df60b2e9309b5fd58a1c694d47
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

maintainers.rst

@@ -171,6 +171,7 @@ Xilinx platform port
 .. _rockchip-linux: https://github.com/rockchip-linux
 .. _shawnguo2: https://github.com/shawnguo2
 .. _sivadur: https://github.com/sivadur
+.. _smaeul: https://github.com/smaeul
 .. _soby-mathew: https://github.com/soby-mathew
 .. _TonyXie06: https://github.com/TonyXie06
 .. _vwadekar: https://github.com/vwadekar