device: Add unit to Kconfig option name: PRE_GRAPHICS_DELAY_MS

It’s good practice to put the unit into the name.

Change-Id: I1493f61d4e495c22f09abf1829bb2eab9b1fd2b6
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50517
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

Documentation/getting_started/kconfig.md

@@ -607,7 +607,7 @@ int <expr> \[if <expr>\]
 
 
 ##### Example:
-    config PRE_GRAPHICS_DELAY
+    config PRE_GRAPHICS_DELAY_MS
         int "Graphics initialization delay in ms"
         default 0
         help