[yocto] BKM on add SRC_URI MD5 and SHA256 checksum

[Yu, Ke]

Hi Distro folks:

As Saul suggest to add SRC_URI MD5 and SHA256 checksum when we upgrade the recipes, here is a simple how-to:

Two entry is needed for checksum, take meta/recipes-extended/tar/tar_1.23.bb as example:
SRC_URI[md5sum] = "41e2ca4b924ec7860e51b43ad06cdb7e"
SRC_URI[sha256sum] = "c9328372db62fbb1d94c9e4e3cefc961111af46de47085b635359c00a0eebe36"

The md5sum and sha256sum value can be get by:

# md5sum /your_DL_DIR/ tar-1.23.tar.bz2
41e2ca4b924ec7860e51b43ad06cdb7e

# sha256sum /your_DL_DIR/ tar-1.23.tar.bz2
c9328372db62fbb1d94c9e4e3cefc961111af46de47085b635359c00a0eebe36

Regards
Ke