ARM platforms: use auto-generated kernel_devices

Note that the auto-generated kernel_devices will differ slightly from
the ones present in the kernel until now. When devices have
registers that aren't page-aligned we now always set the appropriate
PPTR to be the start address of the device, while previously the PPTR
was sometimes page-aligned.

Specifically, this change to PPTRs affects:
- bcm2837 intc
- bcm2837 uart
- allwinnerA20 timer