scripts: add u-boot directory. [1/2]

PD#SWPL-102140

Problem:
add mcuboot for RTOS.

Solution:
add u-boot directory.

Verify:
N/A

Change-Id: I5b24e0c6dadb411a72bef1090397228e32c3b10e
Signed-off-by: shijie.xiong <shijie.xiong@amlogic.com>
1 file changed