crypto: remove redundant convert_key_to_hex_ascii call

- Breaks decryption on some hw_crypto devices
- Default value already defined in preceding ifdef
- PS2: Move crypt_params definition prior to ifdef
  (matches corresponding code from CAF)

Huge thanks to @beaups for figuring out the issue!

Change-Id: I1fd4e3a4862f022b17a555773feb1d6deac9d34c