No section mismatch warnings for Thumb2 kernels

After some time investigating why I wasn't seeing some kernel section mismatch errors that someone else was seeing, I found the cause was that in Linaro we build Thumb2 kernels in the main, and modpost.c doesn't have support for any of the Thumb relocation types in addend_arm_rel().

I thought I would spread this knowledge, because lack of section mismatch warnings means we might miss some nasty bugs when developing code.

If this is old news, then sorry for the noise.