Revert "Update to v5.18 kernel headers."

Revert "Update to v5.18 kernel headers."

Revert submission 2106847-kernel_update

Reason for revert: b/234125620
Reverted Changes:
I5844ca1fc:Update to v5.18 kernel headers.
I5700813ee:Update to v5.18 kernel headers.
Bug: 234125620

Change-Id: I07a39aa9c01939455b5a2a9da5fc04be497ca399
diff --git a/libc/kernel/uapi/asm-generic/signal.h b/libc/kernel/uapi/asm-generic/signal.h
index 5cb1dce..874fece 100644
--- a/libc/kernel/uapi/asm-generic/signal.h
+++ b/libc/kernel/uapi/asm-generic/signal.h
@@ -84,7 +84,7 @@
 typedef struct sigaltstack {
   void __user * ss_sp;
   int ss_flags;
-  __kernel_size_t ss_size;
+  size_t ss_size;
 } stack_t;
 #endif
 #endif