soc/x86/intel_quark: remove support for Quark D2000 SoC

Removed Quark D2000 SoC files and first-order related DT bindings.

A few config options have been moved from the CONFIG_* space to
the DT_* space, as they were defined in the D2000 Kconfig files
and "leaked" into the other Quark trees.

Signed-off-by: Charles E. Youse <charles.youse@intel.com>