mmc: sh_mmcif: correctly report success when obtaining DMA channels

mmc: sh_mmcif: correctly report success when obtaining DMA channels

The debug message could still report success when getting the channels
was OK but configuring them failed. This actually caused a minor detour
when debugging DMA problems, so make sure the success is only reported
when the channels are really ready-to-use.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20240928094454.3592-2-wsa+renesas@sang-engineering.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>