witherspoon-128: Remove mbox node from device tree

The mbox device driver was never upstreamed and has been dropped
from the linux tree. Remove the node from the witherspoon-128 system
as it has already been removed from the upstreamed systems.
Also rebase the patch on top of the latest linux dev-5.2 branch.

Change-Id: Ic608886103d0e68373fecdef540311e7c48b7ad8
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
1 file changed