ptp: uapi: change _IOW to IOWR in PTP_SYS_OFFSET_EXTENDED definition

The ioctl command is read/write (or just read, if the fact that user space
writes n_samples field is ignored).
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/ptp_clock.h

@@ -147,7 +147,7 @@ struct ptp_pin_desc {
 #define PTP_SYS_OFFSET_PRECISE \
 	_IOWR(PTP_CLK_MAGIC, 8, struct ptp_sys_offset_precise)
 #define PTP_SYS_OFFSET_EXTENDED \
-	_IOW(PTP_CLK_MAGIC, 9, struct ptp_sys_offset_extended)
+	_IOWR(PTP_CLK_MAGIC, 9, struct ptp_sys_offset_extended)
 
 struct ptp_extts_event {
 	struct ptp_clock_time t; /* Time event occured. */