dmaengine: tegra: Use struct for register offsets

dmaengine: tegra: Use struct for register offsets

Repurpose the struct tegra_dma_channel_regs to define offsets for all the
channel registers. Previously, the struct only held the register values
for each transfer and was wrapped within tegra_dma_sg_req. Move the
values directly into tegra_dma_sg_req and use channel_regs for
storing the register offsets. Update all register reads/writes to use
the struct channel_regs. This prepares for the register offset change
in Tegra264.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://patch.msgid.link/20260331102303.33181-6-akhilrajeev@nvidia.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>