irqdomain: Improve diagnostics when a domain mapping fails

When the map operation fails log the error code we get and add a WARN_ON()
so we get a backtrace (which should help work out which interrupt is the
source of the issue).

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>