[][Refactor prepare.sh]

[Description]
Refactor prepare.sh
1. read branch version from feeds.conf.default_ori if exist(do autobuild script)
2. read branch version from feeds.conf.default if (1) not exist(do prepare.sh only)

[Release-log]
N/A

Change-Id: I8b24e6bc19b13d6866fff3c1d978369ffd7dbbd1
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5228909
1 file changed