Add new entry to customize bitbake conf document
Add new entry to customize bitbake conf document

 * SSTATE_DIR
 * DL_DIR

Signed-off-by: Ronan Le Martret <18c24d1e59fd6c0a745b9d66ccd59271e1af72fe@iot.bzh>

leon-anavi/docs-agl,automotive-grade-linux/docs-agl,leon-anavi/docs-agl,automotive-grade-linux/docs-agl,claneys/docs-agl,leon-anavi/docs-agl,automotive-grade-linux/docs-agl,claneys/docs-agl,claneys/docs-agl,claneys/docs-agl,automotive-grade-linux/docs-agl,leon-anavi/docs-agl