MdeModulePkg/SdMmcPciHcDxe: allow HC capabilities to be overridden

Invoke the newly introduced SD/MMC override protocol to override
the capabilities register after reading it from the device registers,
and to call the pre/post host init and reset hooks at the appropriate
times.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>