vfio: fix boundary check in region search
vfio: fix boundary check in region search

A previously mapped region is skipped during the search, leading to
DMA unmap fails.

This patch fixes it and rewords the comment.

Fixes: 73a639085938 ("vfio: allow to map other memory regions")

Signed-off-by: Xiao Wang <28aecb4e45c1566b6185c24680691da84bd4fcf8@intel.com>
Acked-by: Anatoly Burakov <814e00d8f6e4e81b7ccc7e3e5a0bfec0078f0203@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk