[ARM] Add a reference from struct device to the dma bounce info

[ARM] Add a reference from struct device to the dma bounce info

dmabounce keeps a per-device structure, and finds the correct
structure by walking a list.  Since architectures can now add
fields to struct device, we can attach this structure direct to
the struct device, thereby eliminating the code to search the
list.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>