drivers: timer: intel_adsp: Update driver to use dts Kconfig symbol

Update Intel ADSP timer driver to use DT_HAS_<compat>_ENABLED Kconfig
symbol to expose the driver and enable it by default based on
devicetree.

We remove setting 'default y' for the timer driver in
Kconfig.defconfig.series as that is now handled in the driver Kconfig.

Signed-off-by: Kumar Gala <kumar.gala@intel.com>