Unnecessary operation removed from map() in WMath.cpp (espressif#6218)

* Unneccesary Operation Removed

(A) extra operation not needed and incorrect:
      wrong by 0.5 but happens to be thrown out

     ( delta * dividend + (divisor / 2) ) / divisor

        delta * dividend     divisor
    = ---------------- + -----------
        divisor                    2 * divisor

    = delta * dividend / divisor + 1/2

(B) check first before doing other computations

(C) changed to rise/run, easier for future maintainer
      since it's closer to equation of a line

(D) before: mult, shift, add, div, add
      now: mult, div, add

(E) error message easier to trace where thrown

* Update WMath.cpp

forgot to change variable name

Author: IanSC

cores/esp32/WMath.cpp

@@ -67,14 +67,14 @@ long random(long howsmall, long howbig)
 }
 
 long map(long x, long in_min, long in_max, long out_min, long out_max) {
-    const long dividend = out_max - out_min;
-    const long divisor = in_max - in_min;
-    const long delta = x - in_min;
-    if(divisor == 0){
-        log_e("Invalid map input range, min == max");
-        return -1; //AVR returns -1, SAM returns 0
+    const long run = in_max - in_min;
+    if(run == 0){
+        log_e("map(): Invalid input range, min == max");
+        return -1; // AVR returns -1, SAM returns 0
     }
-    return (delta * dividend + (divisor / 2)) / divisor + out_min;
+    const long rise = out_max - out_min;
+    const long delta = x - in_min;
+    return (delta * rise) / run + out_min;
 }
 
 uint16_t makeWord(uint16_t w)