MIPS: BMIPS: Explicitly configure reset vectors prior to secondary boot

The secondary CPU's reset vector needs to be set to KSEG1 for a cold
boot (release from reset), or KSEG0 for a warm restart.  On a cold boot
KSEG0 may be unavailable (BMIPS4380), and on a warm restart KSEG1 may
be unavailable (XKS01 mode on 4380 or 5000).

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: f.fainelli@gmail.com
Cc: mbizon@freebox.fr
Cc: jogo@openwrt.org
Cc: jfraser@broadcom.com
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8161/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>