This patch factors out the code, which handles the Bonito system
controller. The case of not supporting the DMA coherency is handled
separately to make the logic obvious. Besides, a couple of empty
lines added to beautify the code even further.

No functional changes introduced.
Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>