gpg: Cleanup of dek_to_passphrase function (part 1).
* g10/passphrase.c (passphrase_to_dek_ext): Remove args CUSTDESC and CUSTPROMPT. Merge into the passphrase_to_dek wrapper. (passphrase_get): Remove args CUSTOM_DESCRIPTION and CUSTOM_PROMPT.
The function is nowadays only used for symmetric encryption. Thus we
do not need all the former advanced stuff.
- Signed-off-by: Werner Koch <wk@gnupg.org>