PCI: dwc: Fix ATU identification for designware version >= 4.80

Synopsys designware version >= 4.80 uses a separate register space
for programming ATU. The current code identifies if there exists a
separate register space by accessing the register address of ATUs
in designware version < 4.80. Accessing this address results in
abort in the case of K2G.

Fix it here by adding "version" member to struct dw_pcie. This should be
set by platform specific drivers and designware core will use it to
identify if the platform has a separate ATU space. For platforms which
have not populated the version member, the old method of identification
will still be used.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>