vt: add /dev/vcsu* to devices.txt

Also mention that the traditional devices provide glyph values whereas
/dev/vcsu* is unicode based.
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/admin-guide/devices.txt

@@ -173,14 +173,18 @@
 		they are redirected through the parport multiplex layer.
 
    7 char	Virtual console capture devices
-		  0 = /dev/vcs		Current vc text contents
-		  1 = /dev/vcs1		tty1 text contents
+		  0 = /dev/vcs		Current vc text (glyph) contents
+		  1 = /dev/vcs1		tty1 text (glyph) contents
 		    ...
-		 63 = /dev/vcs63	tty63 text contents
-		128 = /dev/vcsa		Current vc text/attribute contents
-		129 = /dev/vcsa1	tty1 text/attribute contents
+		 63 = /dev/vcs63	tty63 text (glyph) contents
+		 64 = /dev/vcsu		Current vc text (unicode) contents
+		65 = /dev/vcsu1		tty1 text (unicode) contents
 		    ...
-		191 = /dev/vcsa63	tty63 text/attribute contents
+		127 = /dev/vcsu63	tty63 text (unicode) contents
+		128 = /dev/vcsa		Current vc text/attribute (glyph) contents
+		129 = /dev/vcsa1	tty1 text/attribute (glyph) contents
+		    ...
+		191 = /dev/vcsa63	tty63 text/attribute (glyph) contents
 
 		NOTE: These devices permit both read and write access.