MAINTAINERS: ARM/Amlogic SoCs: add Neil as primary maintainer

Add Neil as primary maintainer for the Amlogic family of Arm SoCs.  I
will now act as co-maintainer.

Neil is already doing lots of the reviewing, testing and behind the
scenes support for users of the upstream kernel on these SoCs, so this
is just to formalize the current state of affairs.

Thanks Neil for all of your efforts, and keep up the great work!

Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20210511190054.26300-1-khilman@baylibre.com

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>