dt-bindings: sdhci-fujitsu: document cmd-dat-delay property

Document a new boolean property of the sdhci-fujitsu binding that
indicates whether the CMD_DAT_DELAY bit needs to be set in the
F_SDH30_ESD_CONTROL register.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>