soc: Add Amlogic SoC Information driver

Amlogic SoCs have a SoC information register for SoC type, package type and
revision information.
This patchs adds support for this register decoding and exposing with the
SoC bus infrastructure.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>