Fixes the following build problem:

arch/mips/sibyte/sb1250/bus_watcher.c: In function 'sibyte_bw_int':
arch/mips/sibyte/sb1250/bus_watcher.c:179:7: error: unused variable 'bw_buf'
[-Werror=unused-variable]
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: sibyte-users@bitmover.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5481/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>