x86/mm: Remove stale comment about KMEMCHECK

This comment referred to a conditional call to kmemcheck_hide() that was
here until commit 49502766 ("kmemcheck: remove annotations").

Now that kmemcheck has been removed, it doesn't make sense anymore.
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180219175039.253089-1-jannh@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/fault.c

@@ -1248,10 +1248,6 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	tsk = current;
 	mm = tsk->mm;
 
-	/*
-	 * Detect and handle instructions that would cause a page fault for
-	 * both a tracked kernel page and a userspace page.
-	 */
 	prefetchw(&mm->mmap_sem);
 
 	if (unlikely(kmmio_fault(regs, address)))