iwlwifi: pcie: dump stack on NIC error in sync commands

Many times, a NIC error is the result of a bad command sent
to the device. If the command was sent synchronously, then
we'll currently print a message when the command is aborted
containing the command. It can be very useful to also see
the stack dump though, so also print that.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>