linux-user: Add setsockopt(SO_ATTACH_FILTER)

This is needed to be able to run dhclient.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index 2ebe356..5f53a28 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -119,6 +119,18 @@
     uint8_t sa_data[14];
 };
 
+struct target_sock_filter {
+    abi_ushort code;
+    uint8_t jt;
+    uint8_t jf;
+    abi_uint k;
+};
+
+struct target_sock_fprog {
+    abi_ushort len;
+    abi_ulong filter;
+};
+
 struct target_in_addr {
     uint32_t s_addr; /* big endian */
 };