mmc: sdhci-brcmstb: Add support for Command Queuing (CQE)

The latest Arasan controller first used in the 7216 now supports
CQE so enable this feature.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Link: https://lore.kernel.org/r/20200113210706.11972-6-alcooperx@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>