MIPS: Sibyte: Fix bus watcher build for BCM1x55 and BCM1x80.

  CC      arch/mips/sibyte/bcm1480/bus_watcher.o
  CHK     kernel/config_data.h
arch/mips/sibyte/bcm1480/bus_watcher.c: In function ‘check_bus_watcher’:
arch/mips/sibyte/bcm1480/bus_watcher.c:86:82: error: ‘A_SCD_BUS_ERR_STATUS_DEBUG’ undeclared (first use in this function)
arch/mips/sibyte/bcm1480/bus_watcher.c:86:82: note: each undeclared identifier is reported only once for each function it appears in
make[3]: *** [arch/mips/sibyte/bcm1480/bus_watcher.o] Error 1
make[2]: *** [arch/mips/sibyte/bcm1480] Error 2
make[1]: *** [arch/mips/sibyte] Error 2
make: *** [arch/mips] Error 2

The register moved around though it's otherwise the same but because of
the changed address it now also has a different name.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/5514/
Reported-by: Markos Chandras <markos.chandras@imgtec.com>