drivers: nrfwifi: Use Zephyr tooling to load nRF70 FW file

Instead of relying on INCBIN macros which do not properly add
dependencies, e.g., modifying FW file doesn't trigger rebuild.

Use the Zephyr cmake tooling to load the FW patch file as a header.

This also improves memory report where the patch target is clearly
visible instead of a hidden section.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>