fdt: Properly handle "no-map" field in the memory region

fdt: Properly handle "no-map" field in the memory region

Mark the memory region with NOMAP flag instead of completely removing it
from the memory blocks. That makes the FDT handling consistent with the EFI
memory map handling.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210115114544.1830068-2-qperret@google.com
Signed-off-by: Rob Herring <robh@kernel.org>