pci: introduce CONFIG_PCI_INDIRECT_BRIDGE option

The pci_indirect.c file is always compiled when
CONFIG_PCI is defined although the indirect PCI
bridge support is not needed by every board.

Introduce a new CONFIG_PCI_INDIRECT_BRIDGE
config option and only compile indirect PCI
bridge support if this options is enabled.

Also add the new option into the configuration
files of the boards which needs that.

Compile tested for powerpc, x86, arm and nds32.
MAKEALL results:

powerpc:
  --------------------- SUMMARY ----------------------------
  Boards compiled: 641
  Boards with warnings but no errors: 2 ( ELPPC MPC8323ERDB )
  ----------------------------------------------------------
  Note: the warnings for ELPPC and MPC8323ERDB are present even
  without the actual patch.

x86:
  --------------------- SUMMARY ----------------------------
  Boards compiled: 1
  ----------------------------------------------------------

arm:
  --------------------- SUMMARY ----------------------------
  Boards compiled: 311
  ----------------------------------------------------------

nds32:
  --------------------- SUMMARY ----------------------------
  Boards compiled: 3
  ----------------------------------------------------------

Cc: Tom Rini <trini@ti.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
diff --git a/include/configs/ELPPC.h b/include/configs/ELPPC.h
index 220372c..d10f4c1 100644
--- a/include/configs/ELPPC.h
+++ b/include/configs/ELPPC.h
@@ -242,6 +242,7 @@
  * PCI stuff
  */
 #define CONFIG_PCI                                /* include pci support */
+#define CONFIG_PCI_INDIRECT_BRIDGE	/* indirect PCI bridge support */
 #define CONFIG_PCI_PNP                            /* pci plug-and-play */
 #define CONFIG_PCI_HOST         PCI_HOST_AUTO
 #undef  CONFIG_PCI_SCAN_SHOW