[ARC] Deprecate q-class option.

[ARC] Deprecate q-class option.

This option was used to control the short instruction selection.  However,
there is no difference in cycles if we use or not a short instruction,
and always someone wants a smaller program.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (arc_conditional_register_usage): R0-R3 and
	R12-R15 are always in ARCOMPACT16_REGS register class.
	* config/arc/arc.opt (mq-class): Deprecate.
	* config/arc/constraint.md ("q"): Remove dependency on mq-class
	option.
	* doc/invoke.texi (mq-class): Update text.
	* common/config/arc/arc-common.c (arc_option_optimization_table):
	Update list.

testsuite/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* gcc.target/arc/nps400-1.c: Update test.