Update README with list and patchwork locations

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Don't add dummy console property if already in dt.

generic_platform_init() adds this propery by default in commit
9594a715b50c338f1261e88c12c120cf8e5b8bba .  If a platform adds it to the dt,
Sapphire detects multiple dt props and dies.  So don't add it if already
exists in the dt.

Signed-off-by: Ryan Grimm <grimm@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>