[libc] fix the conflict warning of read and write functions

bsp/x86/drivers/floppy.c

@@ -357,7 +357,7 @@ void rt_floppy_init(void)
     device->read = rt_floppy_read;
     device->write = rt_floppy_write;
     device->control = rt_floppy_control;
-    device->user_data = NULL;
+    device->user_data = RT_NULL;
 
     rt_device_register(device, "floppy",
                        RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_REMOVABLE | RT_DEVICE_FLAG_STANDALONE);

components/dfs/src/dfs_posix.c

@@ -110,7 +110,11 @@ RTM_EXPORT(close);
  * @return the actual read data buffer length. If the returned value is 0, it
  * may be reach the end of file, please check errno.
  */
+#ifdef _READ_WRITE_RETURN_TYPE
+_READ_WRITE_RETURN_TYPE read(int fd, void *buf, size_t len) /* some gcc tool chains will use different data structure */
+#else
 ssize_t read(int fd, void *buf, size_t len)
+#endif
 {
     int result;
     struct dfs_fd *d;
@@ -150,7 +154,11 @@ RTM_EXPORT(read);
  *
  * @return the actual written data buffer length.
  */
+#ifdef _READ_WRITE_RETURN_TYPE
+_READ_WRITE_RETURN_TYPE write(int fd, const void *buf, size_t len) /* some gcc tool chains will use different data structure */
+#else
 ssize_t write(int fd, const void *buf, size_t len)
+#endif
 {
     int result;
     struct dfs_fd *d;