MIPS: Lantiq: Fix eiu interrupt loading code

Using of_irq_count to load the irq index from the devicetree is incorrect.
This will cause the kernel to map them regardless, even if they dont
actually get used. Change the code to use of_property_count_u32_elems()
instead which is the correct API to use in this case.

Signed-off-by: John Crispin <john@phrozen.org>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/13601/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>