microblaze: board: Remove compilation warning

Variable is used when CONFIG_SYS_FLASH_CHECKSUM is used.

Warning log:
board.c: In function 'board_init':
board.c:101: warning: unused variable 's'

Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: Stephan Linz <linz@li-pro.net>
1 file changed