httpd: scan_header() put argument on xdata

Saves 2 bytes

httpd/httpd.c

@@ -251,7 +251,7 @@ __xdata uint8_t *skip_boundary(__xdata uint8_t *p)
 }
 
 
-__xdata uint8_t *scan_header(__xdata uint8_t *p)
+__xdata uint8_t *scan_header(__xdata uint8_t * __xdata p)
 {
 	content_type = 0;
 	session = 0;