MAINTAINERS: add drivers/soc/amlogic/ to amlogic list

While sending a patch for drivers/soc/amlogic/Kconfig, I saw that
getmaintainer.pl give nobody for it.  This patchs adds
drivers/soc/amlogic/ to amlogic maintainers.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>