dma: pl330: rip out broken, redundant ID probing

The PL330 driver probes the peripheral and primecell IDs of the device to
make sure that it is indeed an AMBA PL330. However, it does this by
making byte accesses to a device mapping of the word-aligned ID
registers, which is either UNPREDICTABLE or generates an alignment fault
(depending on the presence of the virtualisation extensions).

Rather than fix this code, we can actually rip most of it out and let
the AMBA bus driver correctly do the probing for us.

Cc: Jassi Brar <jaswinder.singh@linaro.org>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Jassi Brar <jaswinder.singh@linaro.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>