OvmfPkg/LsiScsiDxe: Examine the incoming SCSI Request Packet

This is the first part of LsiScsiPassThru(). Before processing the SCSI
Request packet, we have to make sure whether the packet is valid or not.

v2: Make LsiScsiPassThru() return EFI_UNSUPPORTED since this function is
    half-implemented

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200717061130.8881-10-glin@suse.com>

OvmfPkg/LsiScsiDxe/LsiScsi.h

@@ -13,6 +13,10 @@
 #define _LSI_SCSI_DXE_H_
 
 typedef struct {
+  //
+  // The max size of CDB is 32.
+  //
+  UINT8                           Cdb[32];
   //
   // Allocate 64KB for read/write buffer. It seems sufficient for the common
   // boot scenarios.