x86: sandbox: pch: Add a CONFIG option for PCH

At present this uclass is selected only on x86. In order to add a test for
it, it must also support sandbox. Create a new CONFIG_PCH option and
enable it on x86 and sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index e9fbadd..f24351a 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -64,6 +64,8 @@
 
 source "drivers/pci/Kconfig"
 
+source "drivers/pch/Kconfig"
+
 source "drivers/pcmcia/Kconfig"
 
 source "drivers/phy/Kconfig"