[patch,avr] Addendum to PR31124

[Nick Clifton]

Hi Johann,

> This is a small addendum to PR31124 "rodata in flash for
> more AVR devices".
> 
> It adds some symbols so the startup code can set a lock
> on the FLMAP bit field as specified by the user.
> 
> New symbols are introduced because otherwise, all the
> computations / decisions would have to be performed at
> run-time.

Patch approved and applied.

Cheers
   Nick