vexpress64: compile Juno PCIe conditionally

Only compile in PCIe support if the board really uses it. Provide
a __weak stub for the init function if e.g. FVP is being built.

Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/board/armltd/vexpress64/Makefile b/board/armltd/vexpress64/Makefile
index a35db40..b4391a7 100644
--- a/board/armltd/vexpress64/Makefile
+++ b/board/armltd/vexpress64/Makefile
@@ -5,4 +5,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-y	:= vexpress64.o pcie.o
+obj-y	:= vexpress64.o
+obj-$(CONFIG_TARGET_VEXPRESS64_JUNO)	+= pcie.o
diff --git a/board/armltd/vexpress64/pcie.c b/board/armltd/vexpress64/pcie.c
index eb23dd5..b3fb09c 100644
--- a/board/armltd/vexpress64/pcie.c
+++ b/board/armltd/vexpress64/pcie.c
@@ -191,7 +191,5 @@
 
 void vexpress64_pcie_init(void)
 {
-#ifdef CONFIG_TARGET_VEXPRESS64_JUNO
 	xr3pci_init();
-#endif
 }
diff --git a/board/armltd/vexpress64/vexpress64.c b/board/armltd/vexpress64/vexpress64.c
index f4e8084..3add099 100644
--- a/board/armltd/vexpress64/vexpress64.c
+++ b/board/armltd/vexpress64/vexpress64.c
@@ -28,6 +28,13 @@
 	.platdata = &serial_platdata,
 };
 
+/* This function gets replaced by platforms supporting PCIe.
+ * The replacement function, eg. on Juno, initialises the PCIe bus.
+ */
+__weak void vexpress64_pcie_init(void)
+{
+}
+
 int board_init(void)
 {
 	vexpress64_pcie_init();