Fix checking of negative with unsigned variables.
Check digestSz for 0 in wc_SSH_KDF() so that no possibility of dividing
by zero.
Change XMEMCPY to XMEMSET in renesas_sce_util.c.
Fix test.c to free prvTmp and pubTmp on read error.
Remove unused variables.
XFREE checks for NULL so don't check before call.
Move variable declarations to reduce scope.