mmc: host: sdhci-sprd: Add software queue support

Add software queue support to improve the performance.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/f629b32943aae9e30ffa17acf4af06c270417001.1581478569.git.baolin.wang7@gmail.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>