Rename sama5d4_loader and update new sam-ba script

guowenxue

2019-08-23 b047b393eecb0b9aeebb056ef5ee585a99940ba8

linux-bsp/tarballs/linux-at91.tar.xz does not exist in tree 561d99caa7c7741b0d615a83bf2a9cf4311e2016