iwlwifi: fix 3945 ucode info retrieval after failure

When hardware or uCode problem occurs driver captures significant
information from device to enable debugging. The format of this information
is different between 3945 and 4965 and later devices, yet currently the
3945 uses the 4965 and later format. Fix this by adding a new library call
that is initialized to the correct formatting routine based on device.

This moves the iwlagn event and error log handling back to iwl-agn.c to
make it part of iwlagn module.

Also remove the 3945 sysfs file that triggers dump of event log - there is
already a debugfs file that can do it for all drivers.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>