x86/kconfig: Reorganize arch feature Kconfig select's

Peter Zijstra noticed that in arch/x86/Kconfig there are a lot
of X86_{32,64} clauses in the X86 symbol, plus there are a number
of similar selects in the X86_32 and X86_64 config definitions
as well - which all overlap in an inconsistent mess.

So:

  - move all select's from X86_32 and X86_64 to the X64 config
    option

  - sort their names, so that duplications are easier to spot

  - align their if clauses, so that they are easier to identify
    at a glance - and so that weirdnesses stand out more

No change in functionality:

     105 insertions(+)
     105 deletions(-)

Originally-from: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150602153027.GU3644@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>