qshell fix sign-compare

src/drivers/qshell/posix/qshell.cpp

@@ -54,7 +54,7 @@ int QShell::main(std::vector<std::string> argList)
 
 	std::string cmd;
 
-	for (int i = 0; i < argList.size(); i++) {
+	for (size_t i = 0; i < argList.size(); i++) {
 		cmd += argList[i];
 
 		if (i < argList.size() - 1) {
@@ -74,7 +74,7 @@ int QShell::main(std::vector<std::string> argList)
 
 	m_qshell_req.strlen = cmd.size();
 
-	for (int i = 0; i < cmd.size(); i++) {
+	for (size_t i = 0; i < cmd.size(); i++) {
 		m_qshell_req.string[i] = (int) cmd[i];
 	}
 

src/drivers/qshell/qurt/qshell.cpp

@@ -98,7 +98,7 @@ int QShell::main()
 				std::string arg;
 				std::vector<std::string> appargs;
 
-				for (int str_idx = 0; str_idx < m_qshell_req.strlen; str_idx++) {
+				for (size_t str_idx = 0; str_idx < m_qshell_req.strlen; str_idx++) {
 					current_char = m_qshell_req.string[str_idx];
 
 					if (isspace(current_char)) { // split at spaces