EmbeddedPkg/MmcDxe: invoke SetIos() protocol method to set speed and width

EmbeddedPkg/MmcDxe: invoke SetIos() protocol method to set speed and width

Add the interface to change the bus width and speed.

By default, MMC is initialized with 1-bit mode and less than 400KHz bus
clock. It causes MMC working inefficiently.

Set I/O bus width on both MMC controller and EXTCSD. Otherwise, it may
cause unmatched failure case. And support more timing mode, high speed,
HS200 & HS400 mode.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>