ARM: socfpga: add CPU_METHOD_OF_DECLARE for Arria 10

Add boot_secondary implementation for the Arria10 platform. Bringing up
the secondary core on the Arria 10 platform is pretty similar to the
Cyclone/Arria 5 platform, with the exception of the following differences:

- Register offset to bringup CPU1 out of reset is different.
- The cpu1-start-addr for Arria10 contains an additional nibble.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>