USB: usbmon: touch up the documentation

I think this sentence was confusing regarding the possible size
of the data area.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/usbmon.txt

diff --git a/Documentation/usb/usbmon.txt b/Documentation/usb/usbmon.txt
index 6c3c625..4efd847 100644
--- a/Documentation/usb/usbmon.txt
+++ b/Documentation/usb/usbmon.txt
@@ -305,7 +305,7 @@
 pointed by hdr contains the next event structure, and the data buffer contains
 the data, if any. The event is removed from the kernel buffer.
 
-The MON_IOCX_GET copies 48 bytes, MON_IOCX_GETX copies 64 bytes.
+The MON_IOCX_GET copies 48 bytes to hdr area, MON_IOCX_GETX copies 64 bytes.
 
  MON_IOCX_MFETCH, defined as _IOWR(MON_IOC_MAGIC, 7, struct mon_mfetch_arg)