DMA: shdma: fix CHCLR register address calculation

struct sh_dmae_device::chan_reg is a pointer to u32, therefore when adding
offsets to it care should be taken to add offsets in sizeof(u32) units, not
in bytes. This patch corrects such a bug. While at it we also remove the
redundant parameter of the affected function.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>