iwlwifi: keep 3945 and 4965 headers separate

The iwl3945 and iwl4965 devices share some common structure, but with a
lot of difference split all over.  Currently the two drivers share a lot
of headers and use ugly preprocessor magic to manage the difference.

This patch keeps two entirely separate copies of the headers to get rid
of these hacks an ease future development.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>