ddr: altera: sdram: Clean up sdram_mmr_init_full() part 4

Merge sdr_set_*() functions which are just setting registers among
the sea of register setting in sdram_mmr_init_full(). There is no
need to keep them separate this way, there is nothing special about
them.

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