dmaengine: ptdma: Remove unused pointer dma_cmd_cache

The pointer 'struct kmem_cache *dma_cmd_cache' was introduced in commit
'b0b4a6b1 ("dmaengine: ptdma: register PTDMA controller as a DMA
resource")' but it was never used.

Signed-off-by: Eder Zulian <ezulian@redhat.com>
Reviewed-by: Nathan Lynch <nathan.lynch@amd.com>
Link: https://lore.kernel.org/r/20250415121312.870124-1-ezulian@redhat.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>