Use new riscv unistd names for syscall definition.

The 6.11 kernel moved the unistd files that include the system calls.
So update the script to use the new location.

Bug: 369418631

Test: Build riscv target.
Change-Id: Iaba736a3b057678ef1f34370d59a1a32b4022105
diff --git a/libc/kernel/tools/update_all.py b/libc/kernel/tools/update_all.py
index ae89a80..9e5ed42 100755
--- a/libc/kernel/tools/update_all.py
+++ b/libc/kernel/tools/update_all.py
@@ -92,7 +92,8 @@
                      'kernel/uapi/asm-arm/asm/unistd.h',
                      'kernel/uapi/asm-arm/asm/unistd-eabi.h',
                      'kernel/uapi/asm-arm/asm/unistd-oabi.h',
-                     'kernel/uapi/asm-riscv/asm/unistd.h',
+                     'kernel/uapi/asm-riscv/asm/unistd_32.h',
+                     'kernel/uapi/asm-riscv/asm/unistd_64.h',
                      'kernel/uapi/asm-x86/asm/unistd_32.h',
                      'kernel/uapi/asm-x86/asm/unistd_64.h',
                      'kernel/uapi/asm-x86/asm/unistd_x32.h']: