Disable the cascade IRQ in the cascade handler.  This is required to
get the DB1300 working, and also gets rid of all spurious interrupts
previously observed on the DB1200; so Config[OD] can be disabled
again for better performance.
Signed-off-by: NManuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/2708/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>