Fix the lr register on IRQs
Fix the lr register on IRQs

The lr is being incremented for each IRQ so if, say, there's three IRQs
queued and the thread is paused then the vector code would increment the
lr by 12 and we're return to the wrong address.

Will try and find where it's adding it; can't remember if vector code
does it
sam-truscott/tinker-kernel,sam-truscott/tinker-kernel