Ethernut 5 board support

Add support for the Ethernut 5 open hardware design, based
on Atmel's AT91SAM9XE512 SoC.

V4
 - Fix several coding style issues.
 - Move machine type to config file.
 - Remove use of CONFIG_ATMEL_LEGACY.

Signed-off-by: Tim Schendekehl <tim.schendekehl@egnite.de>
diff --git a/boards.cfg b/boards.cfg
index 9869dd6..8280cb9 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -110,6 +110,7 @@
 cpu9G20_nand                 arm         arm926ejs   cpu9260             eukrea         at91        cpu9260:CPU9G20,NANDBOOT
 cpu9G20_128M                 arm         arm926ejs   cpu9260             eukrea         at91        cpu9260:CPU9G20,CPU9G20_128M
 cpu9G20_nand_128M            arm         arm926ejs   cpu9260             eukrea         at91        cpu9260:CPU9G20,CPU9G20_128M,NANDBOOT
+ethernut5                    arm         arm926ejs   ethernut5           egnite         at91        ethernut5:AT91SAM9XE
 top9000eval_xe               arm         arm926ejs   top9000             emk            at91        top9000:EVAL9000
 top9000su_xe                 arm         arm926ejs   top9000             emk            at91        top9000:SU9000
 meesc                        arm         arm926ejs   meesc               esd            at91        meesc:AT91SAM9263,SYS_USE_NANDFLASH