With the refurbish of ARC600' accumulator support, the mlo_operand
doesn't reflect the proper low accumulator register for the newer
ARCv2 accumulator register used by the fma instructions.  Hence,
replace it with accl_operand predicate.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.md (fmasf4_fpu): Use accl_operand predicate.
	(fnmasf4_fpu): Likewise.