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/configs/tbs2910_defconfig b/configs/tbs2910_defconfig
index 4b304f8..0401dc6 100644
--- a/configs/tbs2910_defconfig
+++ b/configs/tbs2910_defconfig
@@ -83,6 +83,7 @@
 CONFIG_MII=y
 CONFIG_PCI=y
 # CONFIG_PCI_PNP is not set
+CONFIG_PCIE_IMX=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_IMX6=y
 CONFIG_DM_RTC=y