arm: socfpga: Move Stratix 10 SDRAM driver to DM

Convert Stratix 10 SDRAM driver to device model.

Get rid of call to socfpga_per_reset() and use reset
framework.

SPL is changed from calling function in SDRAM driver
directly to just probing UCLASS_RAM.

Move sdram_s10.h from arch to driver/ddr/altera directory.

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>