iwlwifi: Handle new firmware file with ucode build number in header

Adding new API version to account for change to ucode file format.  New
header includes the build number of the ucode.  This build number is the
SVN revision thus allowing for exact correlation to the code that
generated it.

The header adds the build number so that older ucode images can also be
enhanced to include the build in the future.

some cleanup in iwl_read_ucode needed to ensure old header not used and
reduce unnecessary references through pointer with the data is already
in heap variable.

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