dmaengine: ioat: init: Correct misspelling of function parameter 'c' for channel

dmaengine: ioat: init: Correct misspelling of function parameter 'c' for channel

Fixes the following W=1 kernel build warning(s):

 drivers/dma/ioat/init.c:608: warning: Function parameter or member 'c' not described in 'ioat_free_chan_resources'
 drivers/dma/ioat/init.c:608: warning: Excess function parameter 'chan' description in 'ioat_free_chan_resources'

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Logan Gunthorpe <logang@deltatee.com>
Link: https://lore.kernel.org/r/20200714111546.1755231-17-lee.jones@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>