drm/imagination: Use cached memory with dma_coherent

drm/imagination: Use cached memory with dma_coherent

The TI k3-j721s2 platform does not allow us to use uncached memory
(which is what the driver currently does) without disabling cache snooping
on the AXI ACE-Lite interface, which would be too much of a performance
hit.

Given the platform is dma-coherent, we can simply force all
device-accessible memory allocations through the CPU cache. In fact, this
can be done whenever the dma_coherent attribute is present.

Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Link: https://lore.kernel.org/r/20250410-sets-bxs-4-64-patch-v1-v6-15-eda620c5865f@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>