Allow ARC target to be configured with --with-cpu=<cpu-name>.

gas	* config.in (TARGET_WITH_CPU): Undefine.
	* configure.ac: Add --with-cpu support, and define in config.h.
	* configure: Regenerate.
	* config/tc-arc.c: Use TARGET_WITH_CPU to select default CPU.
	* NEWS: Mention new configure option.
6 files changed