ACPI: NHLT: Streamline struct naming

Few recently introduced structs are named 'nhlt2' instead of 'nhlt' to
avoid naming conflicts. With duplicate types gone, the conflicts are no
more.

Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>