Name function arguments in libc headers for Studio.

Second batch of headers...

Bug: http://b/64613623
Test: builds
Change-Id: I8eef043dbf32afee8ff814e9d005f46aee8fa21f
diff --git a/libc/include/sys/reboot.h b/libc/include/sys/reboot.h
index df4739e..c0c4860 100644
--- a/libc/include/sys/reboot.h
+++ b/libc/include/sys/reboot.h
@@ -42,8 +42,8 @@
 #define RB_DISABLE_CAD  LINUX_REBOOT_CMD_CAD_OFF
 #define RB_POWER_OFF    LINUX_REBOOT_CMD_POWER_OFF
 
-int reboot(int reboot_type);
+int reboot(int __cmd);
 
 __END_DECLS
 
-#endif /* _SYS_REBOOT_H_ */
+#endif