media: s5p-mfc: Fix memdev DMA configuration

Having of_reserved_mem_device_init() forcibly reconfigure DMA for all
callers, potentially overriding the work done by a bus-specific
.dma_configure method earlier, is at best a bad idea and at worst
actively harmful. If drivers really need virtual devices to own
dma-coherent memory, they should explicitly configure those devices
based on the appropriate firmware node as they create them.

It looks like the only driver not passing in a proper OF platform device
is s5p-mfc, so move the rogue of_dma_configure() call into that driver
where it logically belongs.

Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>