MdeModulePkg: SdMmc: Add delay before eMMC reset
MdeModulePkg: SdMmc: Add delay before eMMC reset

This delay is necessary for eMMC reset to working properly.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Joe Zhou <45487d51a6ea20c2147041c7f002f0af49eb460f@marvell.com>
Signed-off-by: Marcin Wojtas <99c15d92ebc0e182e5c4df7c7e9e30ce96a863df@semihalf.com>
Reviewed-by: Feng Tian <e66bb7e9f36c82a029035c5885acf75500d07e68@intel.com>

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