pci: Support autoconfig in SPL

Allow PCI autoconfig to be handled in SPL, so that we can set it up
correctly for boards which need to do this before U-Boot proper. This
includes qemu-x64_64 which needs to set up the video device while in
32-bit mode.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 84a2ae9..aca439d 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -44,8 +44,13 @@
 	bool "Enable Plug & Play support for PCI"
 	help
 	  Enable PCI memory and I/O space resource allocation and assignment.
+
 	  This is required to auto configure the enumerated devices.
 
+	  This is normally not done in SPL, but can be enabled if devices must
+	  be set up in the SPL phase. Often it is enough to manually configure
+	  one device, so this option can be disabled.
+
 config PCI_REGION_MULTI_ENTRY
 	bool "Enable Multiple entries of region type MEMORY in ranges for PCI"
 	help