BugLink: http://bugs.launchpad.net/bugs/1570124

Simplify the logic that picks MMIO ranges by pulling out the
logic related to trying to lay frame buffer claim on top of where
the firmware placed the frame buffer.
Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Reference: https://lkml.org/lkml/2016/4/5/941Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>