ddr: altera: sequencer: Wrap misc remaining macros

Introduce structure socfpga_sdram_misc_config to wrap the remaining
misc configuration values in board file. Again, introduce a function,
socfpga_get_sdram_misc_config(), which returns this the structure. This
is almost the final step toward wrapping the nasty QTS generated macros
in board files and reducing the pollution of the namespace.

Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Dinh Nguyen <dinguyen@opensource.altera.com>