SRAM patcher: convert sram_ddr_init to use runtime SRAM patcher

Use the runtime SRAM patcher to set register addresses in
sram_ddr_init.  The long symbol names are intended to help
disambiguate the symbols, now that they are global.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>