dmaengine: mmp_pdma: Add clock support

dmaengine: mmp_pdma: Add clock support

Add support for retrieving and enabling an optional clock during
mmp_pdma_probe(). It is optional because in Marvell devices
such as "marvell,pdma-1.0" the clocks property is not a required
property. But in SpacemiT K1 PDMA, "spacemit,k1-pdma" as the dt
binding schema file stated, clocks is required.

Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://lore.kernel.org/r/20250822-working_dma_0701_v2-v5-2-f5c0eda734cc@riscstar.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>