bits/syscall.h: add futex_waitv from linux v5.16
see
linux commit 039c0ec9bb77446d7ada7f55f90af9299b28ca49
futex,x86: Wire up sys_futex_waitv()
linux commit ea7c45fde5aa3e761aaddb7902a31a95cb120e7b
futex,arm: Wire up sys_futex_waitv()
linux commit b3ff2881ba18b852f79f5476d7631940071f1adb
MIPS: syscalls: Wire up futex_waitv syscall
linux commit 6c122360cf2f4c5a856fcbd79b4485b7baec942a
s390: wire up sys_futex_waitv system call
linux commit a0eb2da92b715d0c97b96b09979689ea09faefe6
futex: Wireup futex_waitv syscall