of: irq: fix return when no match found in irqdomain map

Return an error value (currently returning 0) when a match for an
interrupt in the irqdomain map is not found.

Change-Id: I618fd5d6bf0ecbd84cdda74f469514ca7bc55667
Fixes: 0303182e ("of: irq: add helper to remap interrupts to another irqdomain")
Signed-off-by: Lina Iyer <ilina@codeaurora.org>