Update to v5.8 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.8

Test: NA
Change-Id: I2231c877589820fc09800a200cf4ac62ba74b04c
diff --git a/libc/kernel/uapi/asm-arm64/asm/mman.h b/libc/kernel/uapi/asm-arm64/asm/mman.h
index 6c23fb6..ed77d09 100644
--- a/libc/kernel/uapi/asm-arm64/asm/mman.h
+++ b/libc/kernel/uapi/asm-arm64/asm/mman.h
@@ -16,4 +16,8 @@
  ***
  ****************************************************************************
  ****************************************************************************/
+#ifndef _UAPI__ASM_MMAN_H
+#define _UAPI__ASM_MMAN_H
 #include <asm-generic/mman.h>
+#define PROT_BTI 0x10
+#endif