add fatfs through vfs for EVB plus

1. see board\TencentOS_tiny_EVB_MX_Plus\KEIL\fatfs_through_vfs

components/fs/vfs/tos_vfs.c

@@ -1,7 +1,5 @@
 #include "tos_vfs.h"
 
-#if TOS_CFG_VFS_EN > 0u
-
 __API__ int tos_vfs_open(const char *pathname, vfs_oflag_t flags)
 {
     int path_len = 0, ret = -1;
@@ -677,5 +675,3 @@ __API__ int tos_vfs_stat(const char *pathname, vfs_fstat_t *buf)
     return ret;
 }
 
-#endif
-