futex,x86: Wire up sys_futex_waitv()

Wire up syscall entry point for x86 arch, for both i386 and x86_64.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210923171111.300673-18-andrealmeid@collabora.com