Generic/ByteOrderMark: small performance improvement

The BOM character must be the first character of the file. This means
that this sniff only needs to check the file once, but its code
was being executed for each occurrence of the T_INLINE_HTML token.

This commit changes the sniff code to return the number of tokens in all
of its exit points to ensure that PHPCS executes it just a single time
per file.

Author: rodrigoprimo

src/Standards/Generic/Sniffs/Files/ByteOrderMarkSniff.php

@@ -49,13 +49,13 @@ public function register()
      * @param int                         $stackPtr  The position of the current token in
      *                                               the stack passed in $tokens.
      *
-     * @return void
+     * @return int
      */
     public function process(File $phpcsFile, $stackPtr)
     {
         // The BOM will be the very first token in the file.
         if ($stackPtr !== 0) {
-            return;
+            return $phpcsFile->numTokens;
         }
 
         $tokens = $phpcsFile->getTokens();
@@ -68,12 +68,14 @@ public function process(File $phpcsFile, $stackPtr)
                 $error     = 'File contains %s byte order mark, which may corrupt your application';
                 $phpcsFile->addError($error, $stackPtr, 'Found', $errorData);
                 $phpcsFile->recordMetric($stackPtr, 'Using byte order mark', 'yes');
-                return;
+                return $phpcsFile->numTokens;
             }
         }
 
         $phpcsFile->recordMetric($stackPtr, 'Using byte order mark', 'no');
 
+        return $phpcsFile->numTokens;
+
     }//end process()