x86: Rename MMCONF_BASE_ADDRESS and make it common across x86

This setting will be used by more than just ivybridge so make it common.

Also rename it to PCIE_ECAM_BASE which is a more descriptive name.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 90e828a..928fc60 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -356,4 +356,18 @@
 
 source "board/intel/crownbay/Kconfig"
 
+config PCIE_ECAM_BASE
+	hex
+    default 0xe0000000
+	help
+	  This is the memory-mapped address of PCI configuration space, which
+	  is only available through the Enhanced Configuration Access
+	  Mechanism (ECAM) with PCI Express. It can be set up almost
+	  anywhere. Before it is set up, it is possible to access PCI
+	  configuration space through I/O access, but memory access is more
+	  convenient. Using this, PCI can be scanned and configured. This
+	  should be set to a region that does not conflict with memory
+	  assigned to PCI devices - i.e. the memory and prefetch regions, as
+	  passed to pci_set_region().
+
 endmenu