Convert CONFIG_PCIE_IMX to Kconfig

This converts the following to Kconfig:
   CONFIG_PCIE_IMX

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index fd22034..0c74f95 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -254,6 +254,10 @@
 	  This compatible is used to find pci controller ep node in Kernel DT
 	  to complete fixup.
 
+config PCIE_IMX
+	bool "i.MX PCIe support"
+	depends on ARCH_MX6
+
 config PCIE_INTEL_FPGA
 	bool "Intel FPGA PCIe support"
 	help