util: unbreak futex_wait declaration on FreeBSD after unifying prototypes
Regressed by 095dfc6c. My mistake when rebasing against e3a8013d. CC @unrelentingtech
src/util/futex.c:73:5: error: conflicting types for 'futex_wait'
int futex_wait(uint32_t *addr, int32_t value, struct timespec *timeout)
^
src/util/futex.h:50:5: note: previous declaration is here
int futex_wait(uint32_t *addr, int32_t value, const struct timespec *timeout);
^