Documentation, add kernel-parameters.txt entry for dis_ucode_ldr

dis_ucode_ldr was introduced in 65cef13 ("x86, microcode: Add a disable
chicken bit") and will disable microcode loading on x86.  This kernel
parameter is buried in the code and should be added to the Documentation.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d6f045..34f2afb 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -910,6 +910,8 @@
 			Disable PIN 1 of APIC timer
 			Can be useful to work around chipset bugs.
 
+	dis_ucode_ldr	[X86] Disable the microcode loader.
+
 	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
 			this option disables the debugging code at boot.