plat/qemu: add BT and IPMI support
plat/qemu: add BT and IPMI support

This brings the qemu platform to the level of an Open Power platform.
It adds the BT device used to communicate with the BMC using IPMI
messaging, power_downs and reboots the way OpenPower systems operate.

The device tree is also checked for UART and RTC device nodes and
updated if qemu has not defined them already. The initialization of
the BT and IPMI interfaces depends on the availability of the BT
device which needs to be explicitly defined by qemu. These tests
enable skiboot to maintain compatibility with previous versions of
qemu which did not update the device tree with enabled devices.

Signed-off-by: Cédric Le Goater <2d8cace2254d4e43578d21933db015d84bcc468a@kaod.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,qemu/skiboot,mikey/skiboot,stewart-ibm/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,qemu/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,mikey/skiboot,legoater/skiboot,open-power/skiboot,stewart-ibm/skiboot,open-power/skiboot,stewart-ibm/skiboot