shmem: Remove pid argument of shmem_wait_and_open()

It's unused and it's rewritten in shmem_wait_and_open(),
and it just confuses a reader. So, kill it.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>

criu/shmem.c

@@ -436,7 +436,7 @@ int collect_shmem(int pid, struct vma_area *vma)
 	return 0;
 }
 
-static int shmem_wait_and_open(int pid, struct shmem_info *si, VmaEntry *vi)
+static int shmem_wait_and_open(struct shmem_info *si, VmaEntry *vi)
 {
 	char path[128];
 	int ret;
@@ -515,7 +515,7 @@ static int open_shmem(int pid, struct vma_area *vma)
 	BUG_ON(si->pid == SYSVIPC_SHMEM_PID);
 
 	if (si->pid != pid)
-		return shmem_wait_and_open(pid, si, vi);
+		return shmem_wait_and_open(si, vi);
 
 	if (si->fd != -1) {
 		f = dup(si->fd);