Kernel compatibility fixes

[bwh-mind]

Fix build failures with some of the older stable branches:

• Fix eth_hw_addr_set() definition for compatibility with stable branches
• Make use of MODULE_IMPORT_NS conditional

With these changes, I was able to build for an x86_64 defconfig build of:

• Last stable update for 4.9
• Current stable updates of 4.14, 4.19, 5.4, 5.10, 5.15, 6.1, and 6.5
• 6.6