Rockbox

ROLO currently fails on these targets unless a Rockbox image is being loaded that is sufficiently similar to the one already in memory.

The sequence goes like this:

- rolo_load() loads the new image to audiobuf
- rolo_restart() copies the new image to the start of DRAM (to achieve this without crashing, this function is in .icode)
- rolo_restart() tries to call invalidate_idcache(), but since invalidate_idcache() is in DRAM this fails as the function has been overwritten.

There are several solutions to this:

1) Move invalidate_idcache() into .icode (easy but won't fix all targets, esp. those that don't use IRAM)

2) Create a new .safecode section at the end of DRAM, and move these functions into it (lots of work to update every app.lds and crt0.S, and test every target)

3) Introduce target-specific rolo_restart() functions, as per imx31/rolo_restart.S (less work, as only one should be required per architecture, eg ARMv4/5 etc.)

I'm not sure which of those options is "best". 1) is certainly the easiest, but 2) and 3) should also allow ROLO to work on targets that don't use IRAM.