Update system header includes in fvt_controller.cc

- Remove deprecated <error.h> include
- Add <system_error> for std::system_error
- Add <cerrno> for errno handling
- Streamline and modernize system header includes

fvt_controller.cc

@@ -15,12 +15,13 @@
 #include "config.h"
 #include "fvt_controller.h"
 
-#include <error.h>
 #include <fcntl.h>
 #include <math.h>
 #include <stdint.h>
 
 #include <atomic>
+#include <system_error>  // for std::system_error
+#include <cerrno>       // for errno
 #undef NDEBUG
 #include <cassert>
 #include <cstring>