linux-user: pass correct parameter to do_shmctl()

Fix shmctl issue by passing correct parameter buf to do_shmctl().

Signed-off-by: Petar Jovanovic <petar.jovanovic@imgtec.com>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5702d4e..efd1453 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3215,7 +3215,7 @@
 
 	/* IPC_* and SHM_* command values are the same on all linux platforms */
     case IPCOP_shmctl:
-        ret = do_shmctl(first, second, third);
+        ret = do_shmctl(first, second, ptr);
         break;
     default:
 	gemu_log("Unsupported ipc call: %d (version %d)\n", call, version);