of: partitions: flag partitions from a partition table
We are going to call the of_partition_fixup for regular block
devices like MMC/SD aswell. Add a flag to partitions indicating
they are instanciated from a on-disk partition table so that they
won't be added as device tree partitions during fixup.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>