x86: clean up mce= argument parsing slightly

Move the = into the __setup line.
Document the option in kernel-parameters.txt by adding a pointer
to the x86-64 specific documentation.

[ tglx: arch/x86 adaptation ]

Pointed out by Robert Day
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 63bda363..98cf90f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -994,6 +994,8 @@
 
 	mce		[X86-32] Machine Check Exception
 
+	mce=option	[X86-64] See Documentation/x86_64/boot-options.txt
+
 	md=		[HW] RAID subsystems devices and level
 			See Documentation/md.txt.