Update cv25519 decrypt function

[cedelavergne-ledger]

1st step to fix cv25519 decryption.
Now the code doesn't return CX_INVALID_CURVE anymore.

Remaining an issue show on the PC side:

gpg: public key is 551E384EA3608B44
gpg: no running gpg-agent - starting '/usr/bin/gpg-agent'
gpg: waiting for the agent to come up ... (5s)
gpg: connection to agent established
gpg: using subkey 551E384EA3608B44 instead of primary key BA8BF32C7557C015
gpg: pinentry launched (46842 gnome3 1.1.1 /dev/pts/2 xterm-256color :0 20620/1000/5 1000/1000 -)
gpg: ecdh failed in gcry_cipher_decrypt: Checksum error
gpg: using subkey 551E384EA3608B44 instead of primary key BA8BF32C7557C015
gpg: encrypted with 255-bit ECDH key, ID 551E384EA3608B44, created 2024-03-15
      "testkey"
gpg: public key decryption failed: Checksum error
gpg: decryption failed: No secret key
Decryption error!

Checklist

• App update process has been followed
• Target branch is develop
• Application version has been bumped

[ledger-wiz-cspm-secret-detection]

Wiz Scan Summary

IaC Misconfigurations
Total
Secrets

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 27.01%. Comparing base (400ff19) to head (db129e4).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #103   +/-   ##
========================================
  Coverage    27.01%   27.01%           
========================================
  Files            1        1           
  Lines          211      211           
========================================
  Hits            57       57           
  Misses         154      154           

Flag	Coverage Δ
unittests	27.01% <ø> (ø)

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