Read the CPU IRQ line reportedly used for the Fast Debug Channel (FDC)
interrupt from the IntCtl register and store it in cp0_fdc_irq where
platform implementations of the new weak platform function
get_c0_fdc_int() can refer to it.

[ralf@linux-mips.org: Fixed conflict.]
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/9140/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>