x86/mm/pkeys: Add Kconfig prompt to existing config option

x86/mm/pkeys: Add Kconfig prompt to existing config option

I don't have a strong opinion on whether we need this or not.
Protection Keys has relatively little code associated with it,
and it is not a heavyweight feature to keep enabled.  However,
I can imagine that folks would still appreciate being able to
disable it.

Here's the option if folks want it.

Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>