linux-user: do_shmdt(): Fix page_set_flags's 2nd arg.

2nd arg of page_set_flags() should be start+size, but size.
Signed-off-by: NTakashi YOSHII <takasi-y@ops.dti.ne.jp>
Acked-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

linux-user/syscall.c

@@ -2752,7 +2752,7 @@ static inline abi_long do_shmdt(abi_ulong shmaddr)
     for (i = 0; i < N_SHM_REGIONS; ++i) {
         if (shm_regions[i].start == shmaddr) {
             shm_regions[i].start = 0;
-            page_set_flags(shmaddr, shm_regions[i].size, 0);
+            page_set_flags(shmaddr, shmaddr + shm_regions[i].size, 0);
             break;
         }
     }