crypto_backend: fix type of enc parameter

crypto_backend: fix type of enc parameter

We had parts of a abstraction, but it wasn't consistent.
GCC 13 now complains about the type mismatch with mbedtls now:

crypto_mbedtls.c:568:1: error:
conflicting types for ‘cipher_ctx_init’ due to enum/integer mismatch;
have ‘void(mbedtls_cipher_context_t *, const uint8_t *, const char *, const mbedtls_operation_t)’
[...] [-Werror=enum-int-mismatch]
crypto_backend.h:341:6: note:
previous declaration of ‘cipher_ctx_init’ with type
‘void(cipher_ctx_t *, const uint8_t *, const char *, int)’ [...]

Previous compiler versions did not complain.

v2:
 - clean solution instead of quick solution. Fix the actual API
   definition

Change-Id: If0dcdde30879fd6185efb2ad31399c1629c04d22
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Message-Id: <20240327162621.1792414-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg28498.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>