Datasheet for AT25PE16 specifies the format of the ID1.
The capacity is encoded in 5 bottom bits of the ID1.
AT25SF641B and AT25SF128A both conform to that spec,
presumably other Adesto AT25 ICs as well.

This function will unset the read only status of the
whole flash. This is handy if you want to use an IC from a
salvaged board that has the flash content write protected.
Tested on Winbond 8 MByte IC.

This allows to write files without knowing their file-size
beforehand. When the auto-growing file is being written
no other file can be written. It is important to close
the auto-growing file when the writing is finished.
To create autogrowing file pass 0 as its length.