Update to v6.4 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-6.4

Test: Bionic unit tests pass.
Change-Id: I991f8eaa2b272a464166addb13e6bdc63734444d
diff --git a/libc/kernel/uapi/asm-riscv/asm/unistd.h b/libc/kernel/uapi/asm-riscv/asm/unistd.h
index 665b820..b321ead 100644
--- a/libc/kernel/uapi/asm-riscv/asm/unistd.h
+++ b/libc/kernel/uapi/asm-riscv/asm/unistd.h
@@ -27,3 +27,7 @@
 #define __NR_riscv_flush_icache (__NR_arch_specific_syscall + 15)
 #endif
 __SYSCALL(__NR_riscv_flush_icache, sys_riscv_flush_icache)
+#ifndef __NR_riscv_hwprobe
+#define __NR_riscv_hwprobe (__NR_arch_specific_syscall + 14)
+#endif
+__SYSCALL(__NR_riscv_hwprobe, sys_riscv_hwprobe)