Removed magic numbers in `load.c` for the defines in header.

src/load/load.c

@@ -32,7 +32,7 @@ static bool portb_disabled[8] = {0};
 
 static bool valid_load(uint16_t val)
 {
-    if(val > 527 && val < 1000) {
+    if(val > LOWTHRESH && val < HIGHTHRESH) {
         return true;
     }
     return false;