mmc: host: sdhci-sprd: Implement the request_atomic() API

mmc: host: sdhci-sprd: Implement the request_atomic() API

Implement the request_atomic() API for nonremovable cards, that means
we can submit next request in the irq hard handler context to reduce
latency.

Moreover factor out the AUTO CMD23 checking into a separate function
to reduce duplicate code.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/60142fe6c6c1dbba2696e775564ae2166786f0bc.1586744073.git.baolin.wang7@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>