MINOR: ssl: set functions as static when no protypes in the .h

MINOR: ssl: set functions as static when no protypes in the .h

Check with -Wmissing-prototypes what should be static.

src/ssl_sock.c:1572:5: error: no previous prototype for ‘ssl_sock_sctl_add_cbk’ [-Werror=missing-prototypes]
 1572 | int ssl_sock_sctl_add_cbk(SSL *ssl, unsigned ext_type, const unsigned char **out, size_t *outlen, int *al, void *add_arg)
      |     ^~~~~~~~~~~~~~~~~~~~~
src/ssl_sock.c:1582:5: error: no previous prototype for ‘ssl_sock_sctl_parse_cbk’ [-Werror=missing-prototypes]
 1582 | int ssl_sock_sctl_parse_cbk(SSL *s, unsigned int ext_type, const unsigned char *in, size_t inlen, int *al, void *parse_arg)
      |     ^~~~~~~~~~~~~~~~~~~~~~~
src/ssl_sock.c:1604:6: error: no previous prototype for ‘ssl_sock_infocbk’ [-Werror=missing-prototypes]
 1604 | void ssl_sock_infocbk(const SSL *ssl, int where, int ret)
      |      ^~~~~~~~~~~~~~~~
src/ssl_sock.c:2107:6: error: no previous prototype for ‘ssl_sock_msgcbk’ [-Werror=missing-prototypes]
 2107 | void ssl_sock_msgcbk(int write_p, int version, int content_type, const void *buf, size_t len, SSL *ssl, void *arg)
      |      ^~~~~~~~~~~~~~~
src/ssl_sock.c:3936:5: error: no previous prototype for ‘sh_ssl_sess_new_cb’ [-Werror=missing-prototypes]
 3936 | int sh_ssl_sess_new_cb(SSL *ssl, SSL_SESSION *sess)
      |     ^~~~~~~~~~~~~~~~~~
src/ssl_sock.c:3990:14: error: no previous prototype for ‘sh_ssl_sess_get_cb’ [-Werror=missing-prototypes]
 3990 | SSL_SESSION *sh_ssl_sess_get_cb(SSL *ssl, __OPENSSL_110_CONST__ unsigned char *key, int key_len, int *do_copy)
      |              ^~~~~~~~~~~~~~~~~~
src/ssl_sock.c:4043:6: error: no previous prototype for ‘sh_ssl_sess_remove_cb’ [-Werror=missing-prototypes]
 4043 | void sh_ssl_sess_remove_cb(SSL_CTX *ctx, SSL_SESSION *sess)
      |      ^~~~~~~~~~~~~~~~~~~~~
src/ssl_sock.c:4075:6: error: no previous prototype for ‘ssl_set_shctx’ [-Werror=missing-prototypes]
 4075 | void ssl_set_shctx(SSL_CTX *ctx)
      |      ^~~~~~~~~~~~~
src/ssl_sock.c:4103:6: error: no previous prototype for ‘SSL_CTX_keylog’ [-Werror=missing-prototypes]
 4103 | void SSL_CTX_keylog(const SSL *ssl, const char *line)
      |      ^~~~~~~~~~~~~~
src/ssl_sock.c:5167:6: error: no previous prototype for ‘ssl_sock_deinit’ [-Werror=missing-prototypes]
 5167 | void ssl_sock_deinit()
      |      ^~~~~~~~~~~~~~~
src/ssl_sock.c:6976:6: error: no previous prototype for ‘ssl_sock_close’ [-Werror=missing-prototypes]
 6976 | void ssl_sock_close(struct connection *conn, void *xprt_ctx) {
      |      ^~~~~~~~~~~~~~
src/ssl_sock.c:7846:17: error: no previous prototype for ‘ssl_action_wait_for_hs’ [-Werror=missing-prototypes]
 7846 | enum act_return ssl_action_wait_for_hs(struct act_rule *rule, struct proxy *px,
      |                 ^~~~~~~~~~~~~~~~~~~~~~