pcie: designware: mvebu: do not configure ATU for IO when not used

pcie: designware: mvebu: do not configure ATU for IO when not used

The pcie_dw_mvebu configure ATU regions for memory, configuration
and IO space types. However the latter is not obligatory
and when not specified in the device tree, causes wrong
ATU configuration. Fix that by adding a dependency on the
detected PCIE regions count.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-on: https://sj1git1.cavium.com/18136
Reviewed-by: Kostya Porotchkin <kostap@marvell.com>
Tested-by: Kostya Porotchkin <kostap@marvell.com>