[SPARC]: Remove the broken SUN_AURORA driver.

The SUN_AURORA driver:
- has been marked as BROKEN for more than two years and
- is still marked as BROKEN.

Drivers that had been marked as BROKEN for such a long time seem to be
unlikely to be revived in the forseeable future.

But if anyone wants to ever revive this driver, the code is still
present in the older kernel releases.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David S. Miller <davem@davemloft.net>