iwlwifi: remove copyright and license from Makefiles

We do not generally protect the Makefiles like this.
Remove the details and go with project style.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
X-MFC with: bfcc09ddd422c95a1a2e4e794b63ee54c4902398
X-MFC with: f4c129f5fb1669b284d76a838b1e509f97c2d299