PCI: imx6: Remove redundant of_match_ptr

imx6_pcie_of_match is always compiled in because PCI_IMX6 depends on
SOC_IMX6Q, which only supports OF build.  Hence of_match_ptr is not
required.

[bhelgaas: add changelog details from Shawn]
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Sean Cross <xobs@kosagi.com>