Fixes ATAPI PIO for transfers of greater than one sector,
and centralizes the fix applied for HDD PIO transfers
all in one place, finally.

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For convenience, this branch is available at:
https://github.com/jnsnow/qemu.git branch ide-unify-pio
https://github.com/jnsnow/qemu/tree/ide-unify-pio

This version is tagged ide-unify-pio-v1:
https://github.com/jnsnow/qemu/releases/tag/ide-unify-pio-v1