dmaengine: sun61: fix warning on bad print specfier

The sg_dma_len() returns unsigned int but we had driver print it as %zu, use
%u as documented in Documentation/printk-formats.txt

drivers/dma/sun6i-dma.c: In function ‘sun6i_dma_prep_slave_sg’:
drivers/dma/sun6i-dma.c:643: warning: format ‘%zu’ expects type ‘size_t’,
but argument 8 has type ‘unsigned int’
drivers/dma/sun6i-dma.c:661: warning: format ‘%zu’ expects type ‘size_t’,
but argument 8 has type ‘unsigned int’

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>