MdeModulePkg/SdMmc: Add break to avoid dead loop when polling OCR Reg

MdeModulePkg/SdMmc: Add break to avoid dead loop when polling OCR Reg

At worst case, OCR register may always not set BIT31. It will cause
original code enter to dead loop. Adding a break for such case.

Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>