[][openwrt][common][Add jitterrng package]

[Description]
Add jitterrng package to openwrt.
In this package, there are `init script` and `getrawentropy
source code`.
Init script is using restart test.
Restart test command is `/etc/init.d/jitter_test reload`.
In init script, it utilities the getrawentropy to collect data.
After the `restart test` is over, there are 1000 raw data in `~/`
and jent.tar in `/`.
Otherwise, there is another test that collect 1000000 data in one time.
We can use this command
`getrawentropy -s 1000000 -f /sys/kernel/debug/jitterentropy/noise`.

[Release-log]

Change-Id: I44b063631ee61d34b261a1ae86f9f7c3f60fb035
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8248292
3 files changed