terminal-util: change 2nd parameter of terminal_reset_defensive() to flags

let's convert the 2nd argumeng form a boolean to a proper flags
parameter. Doesn't change behaviour in anyway, but is more readable, and
prepares ground for adding more flags soon.

src/core/exec-invoke.c

@@ -668,7 +668,7 @@ static int setup_confirm_stdio(
         if (r < 0)
                 return r;
 
-        r = terminal_reset_defensive(fd, /* switch_to_text= */ true);
+        r = terminal_reset_defensive(fd, TERMINAL_RESET_SWITCH_TO_TEXT);
         if (r < 0)
                 return r;
 
@@ -4375,7 +4375,7 @@ static void prepare_terminal(
                 if (lock_fd < 0)
                         log_exec_debug_errno(context, p, lock_fd, "Failed to lock /dev/console, ignoring: %m");
 
-                (void) terminal_reset_defensive(STDOUT_FILENO, /* switch_to_text= */ false);
+                (void) terminal_reset_defensive(STDOUT_FILENO, /* flags= */ 0);
         }
 
         (void) exec_context_apply_tty_size(context, STDIN_FILENO, STDOUT_FILENO, /* tty_path= */ NULL);