rk3368 ddr: add configure ddr timing function

rk3368 ddr: add configure ddr timing function

1.add the function of configure ddr timing such us sr_idle, pd_idle, odt
disable frequency, dll bypass frequency, odt strength, driver strength in dts.
2.make sure commit 8be554a50237051e45e ("rk3368 dts: add ddr timing node in
rk3368.dtsi" add ddr timing node in dts that user can configure ddr timing in
dts file.) was merged.
3.bl30 must update to rk3368bl30_v2.11.bin.

Change-Id: Ie8ae559c8128eb01788271a4333c465e21954ab1
Signed-off-by: Tang Yun ping <typ@rock-chips.com>