bootstat: add reboot,longkey sub-reason to known set

regular expression:
- "reboot,longkey,.*" (184)

regex is dependent on:
- https://android-review.googlesource.com/947976

Test: none
Bug: 132955428
Bug: 133520088
Change-Id: I53d13d95ac11ac73273824156363378372a562ed

bootstat/bootstat.cpp

@@ -310,6 +310,7 @@ const std::map<std::string, int32_t> kBootReasonMap = {
     {"shutdown,userrequested,fastboot", 181},
     {"shutdown,userrequested,recovery", 182},
     {"reboot,unknown[0-9]*", 183},
+    {"reboot,longkey,.*", 184},
 };
 
 // Converts a string value representing the reason the system booted to an