Improve max_insns_skipped logic

Improve max_insns_skipped logic

Improve the logic when setting max_insns_skipped.  Limit the maximum size of IT
to MAX_INSN_PER_IT_BLOCK as otherwise multiple IT instructions are needed,
increasing codesize.  Given 4 works well for Thumb-2, use the same limit for ARM
for consistency.

    gcc/
	* config/arm/arm.c (arm_option_params_internal): Improve setting of
	max_insns_skipped.

From-SVN: r251720