utils_random.{c,h}: fix build warning

utils_random.{c,h}: fix build warning

utils_random.c:53:8: warning: no previous prototype for function 'cdrand_d' [-Wmissing-prototypes]
double cdrand_d() {
       ^
./utils_random.h:32:8: note: this declaration is not a prototype; add 'void' to make it a prototype for a zero-parameter function
double cdrand_d();
       ^
                void
utils_random.c:64:10: warning: no previous prototype for function 'cdrand_u' [-Wmissing-prototypes]
uint32_t cdrand_u() {
         ^
./utils_random.h:40:10: note: this declaration is not a prototype; add 'void' to make it a prototype for a zero-parameter function
uint32_t cdrand_u();
         ^
                  void
2 warnings generated.