x86: Add a config for the systemagent PCIEX regions size

Add a way to specify the required size for this region. This is used when
generating ACPI tables.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 76276c6..256a110 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -976,4 +976,22 @@
 
 	  See https://queue.acm.org/blogposting.cfm?id=18977 for more info
 
+config SA_PCIEX_LENGTH
+	hex
+	default 0x10000000 if (PCIEX_LENGTH_256MB)
+	default 0x8000000 if (PCIEX_LENGTH_128MB)
+	default 0x4000000 if (PCIEX_LENGTH_64MB)
+	default 0x10000000
+	help
+	  This option allows you to select length of PCIEX region.
+
+config PCIEX_LENGTH_256MB
+	bool
+
+config PCIEX_LENGTH_128MB
+	bool
+
+config PCIEX_LENGTH_64MB
+	bool
+
 endmenu
diff --git a/arch/x86/cpu/apollolake/Kconfig b/arch/x86/cpu/apollolake/Kconfig
index 99d4e10..37d6289 100644
--- a/arch/x86/cpu/apollolake/Kconfig
+++ b/arch/x86/cpu/apollolake/Kconfig
@@ -13,6 +13,7 @@
 	select TPL_X86_TSC_TIMER_NATIVE
 	select SPL_PCH_SUPPORT
 	select TPL_PCH_SUPPORT
+	select PCIEX_LENGTH_256MB
 	select PCH_SUPPORT
 	select P2SB
 	select SMP_AP_WORK