Remove workaround for register stack overwrite bug in mmix.

Remove workaround for register stack overwrite bug in mmix.

	* config/mmix/mmix.c (mmix_target_asm_function_prologue): Remove
	support for TARGET_REG_STACK_FILL_BUG.
	* config/mmix/mmix.h: Remove member has_call_without_parameters.
	(TARGET_MASK_REG_STACK_FILL_BUG, TARGET_REG_STACK_FILL_BUG):
	Delete.
	(TARGET_DEFAULT): Remove TARGET_MASK_REG_STACK_FILL_BUG.
	(TARGET_SWITCHES): Remove -mreg-stack-fill-bug-workaround and
	-mno-reg-stack-fill-bug-workaround.
	* config/mmix/mmix.md ("call", "call_value"): Don't set struct
	machine member has_call_without_parameters.
	* doc/invoke.texi (Option Summary) <MMIX Options>: Remove
	-mreg-stack-fill-bug-workaround	and
	-mno-reg-stack-fill-bug-workaround.
	(MMIX Options): Ditto.

From-SVN: r49035