patch 8.2.0913: code for resetting v:register is duplicated

Problem:    Code for resetting v:register is duplicated.
Solution:   Add reset_reg_var().

src/normal.c

@@ -1080,16 +1080,7 @@ getcount:
     {
 	clearop(oap);
 #ifdef FEAT_EVAL
-	{
-	    int regname = 0;
-
-	    // Adjust the register according to 'clipboard', so that when
-	    // "unnamed" is present it becomes '*' or '+' instead of '"'.
-# ifdef FEAT_CLIPBOARD
-	    adjust_clip_reg(&regname);
-# endif
-	    set_reg_var(regname);
-	}
+	reset_reg_var();
 #endif
     }