MdePkg UefiScsiLib: Add non-blocking support for SCSI Read/Write command

MdePkg UefiScsiLib: Add non-blocking support for SCSI Read/Write command

Four new functions are added to UefiScsiLib:
ScsiRead10CommandEx
ScsiWrite10CommandEx
ScsiRead16CommandEx
ScsiWrite16CommandEx

They support both blocking and non-blocking SCSI Read/Write operation
depending on the optional parameter 'Event' passed to those APIs.

When 'Event' is NULL, these four functions will call the non-EX version
couterparts to execute blocking SCSI I/O. When 'Event' is not NULL,
non-blocking I/O operation is executed.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19214 6f19259b-4bc3-4df7-8a09-765794883524