p8-i2c: Allow a per-port default timeout
p8-i2c: Allow a per-port default timeout

Add support for setting a default timeout for the I2C port to the
device-tree. This is consumed by skiboot.

Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

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