fs: don't hard code name in validatePosition()

The name of the position being validated by validatePosition()
was not being used. Instead, the string 'position' was being
used everywhere. It worked out because the only call sites were
using the name 'position' as well.

lib/internal/fs/utils.js

@@ -884,17 +884,15 @@ const validateStringAfterArrayBufferView = hideStackFrames((buffer, name) => {
 
 const validatePosition = hideStackFrames((position, name) => {
   if (typeof position === 'number') {
-    validateInteger(position, 'position');
+    validateInteger(position, name);
   } else if (typeof position === 'bigint') {
     if (!(position >= -(2n ** 63n) && position <= 2n ** 63n - 1n)) {
-      throw new ERR_OUT_OF_RANGE('position',
+      throw new ERR_OUT_OF_RANGE(name,
                                  `>= ${-(2n ** 63n)} && <= ${2n ** 63n - 1n}`,
                                  position);
     }
   } else {
-    throw new ERR_INVALID_ARG_TYPE('position',
-                                   ['integer', 'bigint'],
-                                   position);
+    throw new ERR_INVALID_ARG_TYPE(name, ['integer', 'bigint'], position);
   }
 });