PCI: layerscape: Fix arg_count to syscon_regmap_lookup_by_phandle_args()

PCI: layerscape: Fix arg_count to syscon_regmap_lookup_by_phandle_args()

The arg_count parameter to syscon_regmap_lookup_by_phandle_args()
represents the number of argument cells following the phandle. In this
case, the number of arguments should be 1 instead of 2 since the dt
property looks like this:

  fsl,pcie-scfg = <&scfg 0>;

Without this fix, layerscape-pcie fails with the following message on
LS1043A:

  OF: /soc/pcie@3500000: phandle scfg@1570000 needs 2, found 1
  layerscape-pcie 3500000.pcie: No syscfg phandle specified
  layerscape-pcie 3500000.pcie: probe with driver layerscape-pcie failed with error -22

Link: https://lore.kernel.org/r/20250327151949.2765193-1-ioana.ciornei@nxp.com
Fixes: 149fc35734e5 ("PCI: layerscape: Use syscon_regmap_lookup_by_phandle_args")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Roy Zang <Roy.Zang@nxp.com>
Cc: stable@vger.kernel.org