ntb.rst: Fix copy and paste error

It seems the text for the NTB MSI Test Client section was copied from the
NTB Tool Test Client, but was not updated for the new section.  Corrects
the NTB MSI Test Client section text.
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

Documentation/driver-api/ntb.rst

@@ -207,9 +207,9 @@ The MSI test client serves to test and debug the MSI library which
 allows for passing MSI interrupts across NTB memory windows. The
 test client is interacted with through the debugfs filesystem:
 
-* *debugfs*/ntb\_tool/*hw*/
+* *debugfs*/ntb\_msi\_test/*hw*/
 	A directory in debugfs will be created for each
-	NTB device probed by the tool.  This directory is shortened to *hw*
+	NTB device probed by the msi test.  This directory is shortened to *hw*
 	below.
 * *hw*/port
 	This file describes the local port number