Update to v6.8 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-6.8

Test: Builds and bionic unit tests pass on raven.
Test: Able to log in to an Android GO 32 bit device.
Change-Id: I0022cdb20c19726f526acaab2866f1e25794b77e
diff --git a/libc/kernel/uapi/xen/gntalloc.h b/libc/kernel/uapi/xen/gntalloc.h
index 02e4d47..4f0e7b8 100644
--- a/libc/kernel/uapi/xen/gntalloc.h
+++ b/libc/kernel/uapi/xen/gntalloc.h
@@ -13,7 +13,10 @@
   __u16 flags;
   __u32 count;
   __u64 index;
-  __u32 gref_ids[1];
+  union {
+    __u32 gref_ids[1];
+    __DECLARE_FLEX_ARRAY(__u32, gref_ids_flex);
+  };
 };
 #define GNTALLOC_FLAG_WRITABLE 1
 #define IOCTL_GNTALLOC_DEALLOC_GREF _IOC(_IOC_NONE, 'G', 6, sizeof(struct ioctl_gntalloc_dealloc_gref))