Comment 4 for bug 1811216

This changes the fdt_addr_r to 0x03000000. Although the previous number did not work, I believe the fdt_addr_r will have been changed by many users. For example, Ryan Finnie's pi3 images have this set to 0x02008000. So this updated flash-kernel package will stop those images/installations booting (because the pi's config.txt will still be using the old address). This is potentially going to upset a lot of people.