buse.h: use distro's nbd.h instead of copy/paste

buse.h

@@ -8,60 +8,7 @@ extern "C" {
   /* Most of this file was copied from nbd.h in the nbd distribution. */
 #include <linux/types.h>
 #include <sys/types.h>
-
-#define NBD_SET_SOCK	_IO( 0xab, 0 )
-#define NBD_SET_BLKSIZE	_IO( 0xab, 1 )
-#define NBD_SET_SIZE	_IO( 0xab, 2 )
-#define NBD_DO_IT	_IO( 0xab, 3 )
-#define NBD_CLEAR_SOCK	_IO( 0xab, 4 )
-#define NBD_CLEAR_QUE	_IO( 0xab, 5 )
-#define NBD_PRINT_DEBUG	_IO( 0xab, 6 )
-#define NBD_SET_SIZE_BLOCKS	_IO( 0xab, 7 )
-#define NBD_DISCONNECT  _IO( 0xab, 8 )
-#define NBD_SET_TIMEOUT _IO( 0xab, 9 )
-#define NBD_SET_FLAGS _IO( 0xab, 10 )
-
-  enum {
-    NBD_CMD_READ = 0,
-    NBD_CMD_WRITE = 1,
-    NBD_CMD_DISC = 2,
-    NBD_CMD_FLUSH = 3,
-    NBD_CMD_TRIM = 4
-  };
-
-  /* values for flags field */
-#define NBD_FLAG_HAS_FLAGS	(1 << 0)	/* Flags are there */
-#define NBD_FLAG_READ_ONLY	(1 << 1)	/* Device is read-only */
-#define NBD_FLAG_SEND_FLUSH	(1 << 2)	/* Send FLUSH */
-#define NBD_FLAG_SEND_FUA	(1 << 3)	/* Send FUA (Force Unit Access) */
-#define NBD_FLAG_ROTATIONAL	(1 << 4)	/* Use elevator algorithm - rotational media */
-#define NBD_FLAG_SEND_TRIM    (1 << 5) /* send trim/discard */
-
-  /* Magic numbers */
-#define NBD_REQUEST_MAGIC 0x25609513
-#define NBD_REPLY_MAGIC 0x67446698
-
-  /*
-   * This is the packet used for communication between client and
-   * server. All data are in network byte order.
-   */
-  struct nbd_request {
-    __be32 magic;
-    __be32 type;	/* == READ || == WRITE 	*/
-    char handle[8];
-    __be64 from;
-    __be32 len;
-  } __attribute__ ((packed));
-
-  /*
-   * This is the reply packet that nbd-server sends back to the client after
-   * it has completed an I/O request (or an error occurs).
-   */
-  struct nbd_reply {
-    __be32 magic;
-    __be32 error;		/* 0 = ok, else error	*/
-    char handle[8];		/* handle you got from request	*/
-  };
+#include <linux/nbd.h>
 
   struct buse_operations {
     int (*read)(void *buf, u_int32_t len, u_int64_t offset, void *userdata);