brcm63xx: system_layout: WE7202242SA: Adapt to R01 layout

Rename overlayA/B to overlay1/2. This is a breaking change for older R0B boards. New boards (R01) already have overlay1/2 as name for the overlay volumes.

Older boards need to be migrated to the new volume names manually.

There is a migration image available at https://download.iopsys.eu/iopsys/firmware/MIGRATOR/IOP6/DISC/DISC-X-IOPSYS-6.2.0RC1-MIGRATOR-both-R0B-overlay12_rename-and-R01-broken-layout-fix-210623_1335_nand_squashfs_loader_update.pkgtb. It should print the following on serial console during boot. After that only images that come after this merge request can be used.

[    4.535878] init: - preinit -                                                                                            
DISC_FLASH_LAYOUT_FIX: Starting (if it does not print anything, then volumes are already renamed to overlay1/2)             
overlayA                                                                                                                    
DISC_FLASH_LAYOUT_FIX: Renaming: ubirename /dev/ubi0 overlayA overlay1                                                      
overlayB                                                                                                                    
DISC_FLASH_LAYOUT_FIX: Renaming: ubirename /dev/ubi0 overlayB overlay2                                                      
DISC_FLASH_LAYOUT_FIX: Overlay volume names are:                                                                            
Name:        overlay2                                                                                                                                                                                                                                    
Name:        overlay1                                                                                                       
DISC_FLASH_LAYOUT_FIX: Finished

Current names over overlay-volumes can be shown using:

ubinfo --all | grep "overlay"