driver: ram: rockchip: add common code about dram init

Add commond code about rockchip dram init,include print dram info,
capacity detect,config msch timing,config os_regs and so on.

Change-Id: Ie4

driver: ram: rockchip: add common code about dram init

Add commond code about rockchip dram init,include print dram info,
capacity detect,config msch timing,config os_regs and so on.

Change-Id: Ie4223dac31bde290d19627c96088542fcdd5521d
Signed-off-by: YouMin Chen <cym@rock-chips.com>

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