Add tweaks to work in Mambo simulator

Mambo doesn't implement various things such as PBA SCOMs, LPC,
ChipTOD, etc... It also provides a special console hook.

This adds detection of Mambo via the /mambo node, and enables
us to boot all the way to Linux.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Add scripts to run from Mambo

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>