sparc.c (function_arg_partial_nregs): Return 0 for all complex modes whose size is lesser or equal to a word.

	* config/sparc/sparc.c (function_arg_partial_nregs) [TARGET_ARCH64]:
	Return 0 for all complex modes whose size is lesser or equal to
	a word.  Add a ??? comment for the condition used with 16-byte
	aligned modes.

From-SVN: r73194