Fix libata resource conflict for legacy mode

When the libata is trying to handle legacy ide ports (0x1f0 for instance), it
doesn't take care if the resource has childs or not.
The result is that this situation :
0100-01fe : pnp 00:09
  0170-0177 : libata
  01f0-01f7 : libata

is seen as conflict, which is wrong.
The proposed fix is to detect childs and in this case, look at which child is
conflicting.

Signed-off-by: Arnaud Patard <apatard@mandriva.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>