vfio/common: Fix a small boundary issue of a trace

vfio/common: Fix a small boundary issue of a trace

It uses [offset, offset + size - 1] to indicate that the length of range is
size in most places in vfio trace code (such as
trace_vfio_region_region_mmap()) execpt trace_vfio_region_sparse_mmap_entry().
So change it for trace_vfio_region_sparse_mmap_entry(), but if size is zero,
the trace will be weird with an underflow, so move the trace and trace it
only if size is not zero.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Link: https://lore.kernel.org/r/1650100104-130737-1-git-send-email-chenxiang66@hisilicon.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>