bdshemu: Fix MOVS/STOS/LODS/SCAS/CMPS silent no-op at MaxInstructionsCount boundary

[Luchinkin]

The MOVS/STOS/LODS/SCAS/CMPS handlers gate their body on:
while (Context->InstructionsCount < Context->MaxInstructionsCount),
but the outer dispatch loop has already incremented InstructionsCount to the slot it spent on this dispatch. When those values are equal at that moment (e.g. when MaxInstructionsCount == 1), the body is skipped entirely and ShemuEmulate returns SHEMU_SUCCESS with no memory move, no RSI/RDI advance, no RCX decrement, and no flag update.

Switched both handlers to do { ... } while (...) so the first
iteration always runs.