dm: syscon: Don't require a regmap for PCI devices

dm: syscon: Don't require a regmap for PCI devices

At present it is not possible to use the syscon devices for PCI devices
since a regmap is required. Since PCI uses a 3-cell address the conversion
of the 'reg' property to an address always fails. In any case, the regmap
is not useful with PCI since devices are accessed through the PCI bus
which regmap does not support.

Add a special case for PCI syscon devices, so that they don't set up a
regmap.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>