explicit add the cstdint header for clang compile

fix the build errors with the clang15 and onward:
clang++ sendKey.cpp -I . -lpthread -Wall -Wpedantic -Wextra -o sendkey
sendKey.cpp:64:29: error: unknown type name 'uint32_t'
   64 |     buf.bCtrl = static_cast<uint32_t>(ctrl);
         |                             ^

Signed-off-by: Bo He <[email protected]>
Tracked-On: OAM-129122

sendKey.cpp

@@ -17,6 +17,7 @@
 
 #include <string.h>
 #include <iostream>
+#include <cstdint>
 
 #include "sendKey.h"