win32: pair qemu_memalign() with qemu_vfree()

win32: pair qemu_memalign() with qemu_vfree()

Win32 suffers from a very big memory leak when dealing with SCSI devices.
Each read/write request allocates memory with qemu_memalign (ie
VirtualAlloc) but frees it with qemu_free (ie free).
Pair all qemu_memalign() calls with qemu_vfree() to prevent such leaks.

Signed-off-by: Herve Poussineau <[email protected]>
Signed-off-by: Anthony Liguori <[email protected]>