x86/PCI: add description for check_enable_amd_mmconf boot parameter

Describe check_enable_amd_mmconf.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 395d1a0..8a82489 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1735,6 +1735,9 @@
 				root domains (aka PCI segments, in ACPI-speak).
 		nommconf	[X86] Disable use of MMCONFIG for PCI
 				Configuration
+		check_enable_amd_mmconf [X86] check for and enable
+				properly configured MMIO access to PCI
+				config space on AMD family 10h CPU
 		nomsi		[MSI] If the PCI_MSI kernel config parameter is
 				enabled, this kernel boot option can be used to
 				disable the use of MSI interrupts system-wide.