[dts] [v2] doc/dts_gsg: refresh dts guides

[Tu, Lijuan]

> * quick_start: new added for user quick to start DTS
> * user guide: updated and reworked to align with DTS codes
> * other: remove docs which are not match code and target to update next
> release
> 
> Signed-off-by: Lijuan Tu <lijuan.tu at intel.com>
> Signed-off-by: Haiyang Zhao <haiyangx.zhao at intel.com>
> Signed-off-by: hanyingya <yingyax.han at intel.com>

Applied