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/cpu/ivybridge/sdram.c b/arch/x86/cpu/ivybridge/sdram.c
index 4963448..766b385 100644
--- a/arch/x86/cpu/ivybridge/sdram.c
+++ b/arch/x86/cpu/ivybridge/sdram.c
@@ -757,7 +757,7 @@
 		.mchbar = DEFAULT_MCHBAR,
 		.dmibar = DEFAULT_DMIBAR,
 		.epbar = DEFAULT_EPBAR,
-		.pciexbar = CONFIG_MMCONF_BASE_ADDRESS,
+		.pciexbar = CONFIG_PCIE_ECAM_BASE,
 		.smbusbar = SMBUS_IO_BASE,
 		.wdbbar = 0x4000000,
 		.wdbsize = 0x1000,