mmc: dw_mmc-bluefield: Add support for eMMC HW reset

The eMMC RST_N register is implemented as secure register on the BlueField
SoC and controlled by TF-A. This commit sends an SMC call to TF-A for the
eMMC HW reset.

Reviewed-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Liming Sun <limings@nvidia.com>
Link: https://lore.kernel.org/r/2c459196c6867e325f9386ec0559efea464cfdd6.1718213918.git.limings@nvidia.com


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