Fix NVMData on S+; add a new symbol at start of .nvm_data

[dfordivam]

No description provided.

[dfordivam]

I think that it should also be modified there also

@yogh333 I think at this point the size calculation is happening for the mutable portion of flash memory, which can be written by the nvm_write, and is correct; considering that the symbol is used to cover the .rodata section also.

ledger-device-rust-sdk/ledger_device_sdk/link.ld

Line 44 in 6f6aa0a

_nvram_data = .;