ARM: socfpga: add reset for the Arria 10 platform

Since the Arria10's reset register offset is different from the Cyclone/Arria 5,
it's best to add a new DT_MACHINE_START() for the Arria10.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
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v2: use altera_a10_dt_match for the A10 machine desc