[arm] Use standard option parsing code for detecting

Now that the standard CPU and architecture option parsing code is
available in the driver we can use the main CPU and architecture data
tables for driving the automatic enabling of Thumb code.

Doing this requires that the driver script tell the parser whether or
not the target string is a CPU name or an architecture, but beyond
that it is just standard use of the new capabilities.

We do, however, now get some error checking if the target isn't
recognized, when previously we just ignored unknown targets and hoped
that a later pass would pick up on this.

	* config/arm/arm.h (TARGET_MODE_SPECS): Add additional parameter to
	call to target_mode_check describing the type of option passed.
	* common/config/arm/arm-common.c (arm_arch_core_flag): Delete.
	(arm_target_thumb_only): Use arm_parse_arch_option_name or
	arm_parse_cpu_option_name to match parameters against list of
	available targets.
	* config/arm/parsecpu.awk (gen_comm_data): Don't generate
	arm_arch_core_flags data structure.
	* config/arm/arm-cpu_cdata.h: Regenerated.

From-SVN: r249288