Remove hidden __reboot from header

This change is required:
https://android-review.googlesource.com/#/c/70570

Change-Id: Idb991f96a424aa5b0f9e06d9fb787fe8c8530750
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>
diff --git a/libc/include/sys/reboot.h b/libc/include/sys/reboot.h
index df81139..7d202f7 100644
--- a/libc/include/sys/reboot.h
+++ b/libc/include/sys/reboot.h
@@ -42,7 +42,6 @@
 #define RB_POWER_OFF    LINUX_REBOOT_CMD_POWER_OFF
 
 extern int reboot(int  reboot_type);
-extern int __reboot(int, int, int, void *);
 
 __END_DECLS