rk3288: sdram: auto-detect the capacity

Add support for rk3288 dram capacity auto detect, support DDR3 and
LPDDR3, DDR2 is not supported.
The program will automatically detect:
- channel number
- rank number
- column address number
- row address number

The dts file do not need to describe those info after apply this patch.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Simon Glass <sjg@chromium.org>
Tested-by: Vagrant Cascadian <vagrant@debian.org>
Tested-by: Vagrant Cascadian <vagrant@debian.org>