dma: cppi41: add support for suspend and resume

This patch adds support for suspend/resume functionality to the cppi41
DMA driver. The steps necessary to make the system resume properly were
figured out by trial-and-error. The code as it stands now is the
minimum that has to be done to put the musb host system on an AM33xx
system into an operable state after resume.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>