xtensa: Prepend "(use A0_REG)" to sibling call CALL_INSN_FUNCTION_USAGE instead of...

xtensa: Prepend "(use A0_REG)" to sibling call CALL_INSN_FUNCTION_USAGE instead of emitting it as insn at the end of epilogue

No functional changes.

gcc/ChangeLog:

	* config/xtensa/xtensa-protos.h (xtensa_expand_call):
	Add the third argument as boolean.
	(xtensa_expand_epilogue): Remove the first argument.
	* config/xtensa/xtensa.cc (xtensa_expand_call):
	Add the third argument "sibcall_p", and modify in order to prepend
	"(use A0_REG)" to CALL_INSN_FUNCTION_USAGE if the argument is true.
	(xtensa_expand_epilogue): Remove the first argument "sibcall_p" and
	its conditional clause.
	* config/xtensa/xtensa.md (call, call_value, sibcall, sibcall_value):
	Append a boolean value to the argument of xtensa_expand_call()
	indicating whether it is sibling call or not.
	(epilogue): Remove the boolean argument from xtensa_expand_epilogue(),
	and then append emitting "(return)".
	(sibcall_epilogue): Remove the boolean argument from
	xtensa_expand_epilogue().