dmaengine: xilinx_dma: Fix error code format specifier

'err' is a signed int and error codes are typically negative numbers, so
use '%d' instead of '%u' to format the error code in the error message.

Fixes: ba16db36 ("dmaengine: vdma: Add clock support")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>