Add a move from CONST smalls(%val) to GPR.

This allows 'move {CONST, $1}, R3' with a small enough $1 to emit one
instruction (addi) instead of two instructions (addis, ori).  The
CONST token confusingly isn't in the CONST_ALL set.

mach/powerpc/ncg/table

@@ -389,7 +389,7 @@ MOVES
 
 /* Constants */
 
-	from CONST_ALL smalls(%val) to GPR
+	from CONST_ALL + CONST smalls(%val) to GPR
 		gen
 			COMMENT("move CONST_ALL->GPR smalls")
 			addi %2, R0, {CONST, %1.val}