avr32:board.c: fix compile warning

This patch fixes following warning:

---8<---
board.c: In function 'board_init_r':
board.c:257: warning: unused variable 's'
--->8---

Patch de30122bb58fee7b0f94bcfabab595b6ad757336 missed to remove this variable
too.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
1 file changed