x86: Clean up memory model related configs in arch/x86/Kconfig

* Remove bogus dependency on ARCH_SELECT_MEMORY_MODEL from
  ARCH_FLATMEM_ENABLE.  ENABLE configs don't interfere with
  SELECT_MEMORY_MODEL.  They just need to indicate whether the
  specific memory model is supported.

* Relocate HAVE_ARCH_ALLOC_REMAP, ARCH_PROC_KCORE_TEXT and
  ARCH_SPARSEMEM_DEFAULT so that memory model related configs are
  together in consistent order.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>