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/hwcap.h b/libc/kernel/uapi/asm-arm64/asm/hwcap.h
index ebe2fa4..dcca79b 100644
--- a/libc/kernel/uapi/asm-arm64/asm/hwcap.h
+++ b/libc/kernel/uapi/asm-arm64/asm/hwcap.h
@@ -67,4 +67,5 @@
 #define HWCAP2_BF16 (1 << 14)
 #define HWCAP2_DGH (1 << 15)
 #define HWCAP2_RNG (1 << 16)
+#define HWCAP2_BTI (1 << 17)
 #endif