Fix invalid VHDX generation for image larger than 4Gb

• Part of BAT payload location was lost due to invalid BAT entry encoding type (32 bits instead of 64 bits)
• The sequence of PB/SB entries in BAT was broken due to off-by-one index check. It worked for smaller than 4Gb because there were no SB entries in BAT.

MFC after: 1 day