spinlock.h: Clean up includes

1. Removes unused includes
2. Replaces <stdint.h> with <cstdint>

PiperOrigin-RevId: 469705016
Change-Id: Ic32871be93d01436f5538c44321faad7bd2e4511

absl/base/internal/spinlock.h

@@ -29,10 +29,8 @@
 #ifndef ABSL_BASE_INTERNAL_SPINLOCK_H_
 #define ABSL_BASE_INTERNAL_SPINLOCK_H_
 
-#include <stdint.h>
-#include <sys/types.h>
-
 #include <atomic>
+#include <cstdint>
 
 #include "absl/base/attributes.h"
 #include "absl/base/const_init.h"
@@ -41,8 +39,6 @@
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/scheduling_mode.h"
 #include "absl/base/internal/tsan_mutex_interface.h"
-#include "absl/base/macros.h"
-#include "absl/base/port.h"
 #include "absl/base/thread_annotations.h"
 
 namespace absl {