mmc: sdhci-sprd: Implement the get_max_timeout_count() interface

[ Upstream commit 7486831d

 ]

Implement the get_max_timeout_count() interface to set the Spredtrum SD
host controller actual maximum timeout count.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>