[DOCS] Updated odroidx documentation

Signed-off-by: Anup Patel <anup@brainfault.org>
[DOCS] Updated ODroid-X documentation

Signed-off-by: Anup Patel <anup@brainfault.org>
[COMMANDS] Fix printing and updation of string attributes in devtree command

Signed-off-by: Anup Patel <anup@brainfault.org>
[CORE] Add support for specifying boot commands via /choosen device tree node

This patch provides a methode of specifying boot commands via device tree.

We can specify more than one commands as boot command via bootcmd attribute of /choosen node.

In fact, we can also write a small script via bootcmd attribute.

Signed-off-by: Anup Patel <anup@brainfault.org>
Merge remote-tracking branch 'upstream/master' into dev_exynos4