icnss: Update the smp2p node parsing

As the architecture of the smp2p node is changed, the parsing
of the node to get the irq number need to be updated.
This change takes care of the parsing of the DT node to get
smp2p interrupts and reqister for the threaded irq.

Change-Id: I108aab009eb6bbebb1117fcf46693c801260846c
Signed-off-by: Anurag Chouhan <achouhan@codeaurora.org>