ddr: altera: sdram: Introduce socfpga_sdram_config() structure

ddr: altera: sdram: Introduce socfpga_sdram_config() structure

Introduce this seemingly massive structure, which holds required values
of all the registers of the SDRAM controller. The idea here is to avoid
including the sdram.h header file, which is full of ad-hoc macros that
polute the global namespace. Once the cleanup of sdram.c would be complete
and all registers would be loaded from this new socfpga_sdram_config, a
board file will only pass this structure into the sdram.c . This will
hide all the horrors generated by QTS in the board directory.

Signed-off-by: Marek Vasut <marex@denx.de>