doc/mb/lenovo/montevina: Clarify use of bincfg

`bincfg` is not creating anything new, it just converts
from text to binary.

Change-Id: I14e67ee8bc449d171a951f6edeaa9f9d0c04dbe1
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51319
Reviewed-by: Evgeny Zinoviev <me@ch1p.io>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/mainboard/lenovo/montevina_series.md

@@ -88,10 +88,12 @@ $ mv flashregion_0_flashdescriptor.bin.new.new flashregion_0_flashdescriptor.bin
 
 Continue to the [Configuring coreboot](#configuring-coreboot) section.
 
-#### Creating a new flash descriptor using bincfg
+#### Using checked-in flash descriptor via bincfg
 
-There is a tool to generate a modified flash descriptor called **bincfg**. Go to
-`util/bincfg` and build it:
+There is a copy of an X200's flash descriptor checked into the coreboot
+repository. It is supposed to work for the T400/T500 as well. The descriptor
+can be converted back to its binary form using a tool called **bincfg**. Go
+to `util/bincfg` and build it:
 ```console
 $ cd util/bincfg
 $ make
@@ -110,7 +112,7 @@ If your flash is not 8 MiB, you need to change values of `flcomp_density1` and
 +-----------------+-------+-------+--------+
 ```
 
-Then create the flash descriptor:
+Then convert the flash descriptor:
 ```console
 $ make gen-ifd-x200
 ```