olimex/a20_olinuxino: update readme.txt with lime2 info

[Peter: fix typo, s/AllWinner/Allwinner/]
Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/olimex/a20_olinuxino/readme.txt

@@ -3,12 +3,13 @@ A20-OLinuXino-LIME and A20-OLinuXino-MICRO
 Intro
 =====
 
-These are open hardware boards, both based an the AllWinners A20 SoC.
+These are open hardware boards, all based on the Allwinner A20 SoC.
 
 for more details about the boards see the following pages:
  - https://www.olimex.com/Products/OLinuXino/open-source-hardware
  - https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-MICRO/
  - https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-LIME/
+ - https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-LIME2/
 
 The following defconfigs are available:
  - olimex_a20_olinuxino_micro_defconfig