Prevent user to manually activate an already active flash
bank due to otherwise the metadata sequnce numbers become
out of sync.

the error if the user appears to know what he is doing. Used
during Iopsys 4 to 5 migration.

This in effect limited the system to max 999 upgrades.

This i likely a very old bug.

This will make brcm_fw_tool to force writing pureUBI into same flash bank
again and again even if invoked multiple times. This might happen if the
post-rootfs-fixup fails and the user retries again.

brcm_fw_tool: Add backward compatibility with Broadcom 5.02L.03 and Iopsys 4, which doesn't have pureUBI.

common header for all who needs it. This reduces code duplication.

Then later, when it has been commited (become ready), rename it to a final value.

But it's OK if the volume is missing. It should be ignored.

- No need for specifying a UBI volume for the sequence number. The program scans them all automatically.

check the creation is unique and not a symlink.

- Some cleaning.

This is for security reason. Must not overwrite anything else via symlinks.