MIPS: BMIPS: fix hardware interrupt routing for boot CPU != 0

The hardware interrupt routing for boot CPU != 0 is wrong because it
will route all the hardware interrupts to TP0 which is not the one we
booted from. Fix this by properly checking which boot CPU we are booting
from and updating the right interrupt mask for the boot CPU. This fixes
booting on BCM3368 with bmips_smp_emabled = 0.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: blogic@openwrt.org
Cc: jogo@openwrt.org
Cc: cernekee@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/5650/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>