ARM: mx6: Disable PCIe on SABRE Lite/Nitrogen6x

Use of PCIe on SABRE Lite and Nitrogen6x boards
is atypical and requires the use of custom daughter
boards.

Use in U-Boot is even rarer, so this patch removes it from
the standard configuration.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Acked-by: Marek Vasut <marex@denx.de>
diff --git a/include/configs/nitrogen6x.h b/include/configs/nitrogen6x.h
index ac517ce..5bac100 100644
--- a/include/configs/nitrogen6x.h
+++ b/include/configs/nitrogen6x.h
@@ -355,7 +355,6 @@
 /*
  * PCI express
  */
-#define CONFIG_CMD_PCI
 #ifdef CONFIG_CMD_PCI
 #define CONFIG_PCI
 #define CONFIG_PCI_PNP