dmaengine: bcm2835: add additional defines for DMA-registers

dmaengine: bcm2835: add additional defines for DMA-registers

commit e42685d7a7d5afa6278561ffd85c475eae246be3 upstream.

Add additional defines describing the DMA registers
as well as adding some more documentation to those registers.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
[bwh: Backported to 3.16 as dependency of commit 9e528c799d17
 "dmaengine: bcm2835: Fix abort of transactions"]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>