MdeModulePkg/AtaAtapiPassThru: Correct the algo of calculating PRDT number to avoid beyond the boundary of 32 bit.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Tian, Feng <feng.tian@intel.com>
Reviewed-by: Zeng, Star <star.zeng@intel.com>


git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@15667 6f19259b-4bc3-4df7-8a09-765794883524