nds32: delete unused local variable

Fixes the build-time warning:
	board.c: In function 'board_init_r':
	board.c:304: warning: unused variable 's'

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/nds32/lib/board.c

diff --git a/arch/nds32/lib/board.c b/arch/nds32/lib/board.c
index 7121313..f5de266 100644
--- a/arch/nds32/lib/board.c
+++ b/arch/nds32/lib/board.c
@@ -301,7 +301,6 @@
  */
 void board_init_r(gd_t *id, ulong dest_addr)
 {
-	char *s;
 	bd_t *bd;
 	ulong malloc_start;