t-rsa-testparm: fix 'function declaration isn’t a prototype' warning

* cipher/t-rsa-testparm.c (check_rsa_testparm): Define parameters as
void.

Cherry-picked master commit of:
0909186b9e66aa3a8fac7b2571915c45a7bfaeb3

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>