Update to v5.6 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.6

Add a new method for removing structures. This is to deal with the kernel
headers changing some definitions of timeval to __kernel_old_timeval
and itimerval to __kernel_old_itimerval. Remove the __kernel_old_XX
strutures and change the other structures to the previous definitions.

This only works so long as these structures stay the same, if they
diverge, then a different strategy will need to be implemented.

Test: Booted cuttlefish/walleye.
Test: Ran bionic-unit-tests on cuttlefish/walleye.
Change-Id: I0a61f4fa6e4155c602e0414d9b38c2e1637829af
diff --git a/libc/kernel/uapi/linux/if.h b/libc/kernel/uapi/linux/if.h
index 12967f7..0821f2b 100644
--- a/libc/kernel/uapi/linux/if.h
+++ b/libc/kernel/uapi/linux/if.h
@@ -134,6 +134,7 @@
     fr_proto __user * fr;
     fr_proto_pvc __user * fr_pvc;
     fr_proto_pvc_info __user * fr_pvc_info;
+    x25_hdlc_proto __user * x25;
     sync_serial_settings __user * sync;
     te1_settings __user * te1;
   } ifs_ifsu;