efi/arm: Defer probe of PCIe backed efifb on DT systems

efi/arm: Defer probe of PCIe backed efifb on DT systems

The new of_devlink support breaks PCIe probing on ARM platforms booting
via UEFI if the firmware exposes a EFI framebuffer that is backed by a
PCI device. The reason is that the probing order gets reversed,
resulting in a resource conflict on the framebuffer memory window when
the PCIe probes last, causing it to give up entirely.

Given that we rely on PCI quirks to deal with EFI framebuffers that get
moved around in memory, we cannot simply drop the memory reservation, so
instead, let's use the device link infrastructure to register this
dependency, and force the probing to occur in the expected order.

Co-developed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200113172245.27925-9-ardb@kernel.org