dhparams: Fix .c file generation with OpenSSL >= 1.1.1-pre9

dhparams: Fix .c file generation with OpenSSL >= 1.1.1-pre9

Since OpenSSL upstream commit 201b305a2409
("apps/dsaparam.c generates code that is intended to be pasted or included into
an existing source file: the function is static, and the code doesn't include
dsa.h.  Match the generated C source style of dsaparam.") "openssl dhparam -C"
generates the get_dh functions as static, but the functions are used inside
stream-ssl.c and so the static keyword cannot be used.

This commit removes the static keyword from the get_dh functions during
dhparams.c file generation by restoring the current behaviour.

Signed-off-by: Timothy Redaelli <tredaelli@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>