nrf: Disable FAT/VFS by default.
Most boards don't have an SD card so it makes no sense to have it
enabled. It can be enabled per board (mpconfigboard.h).
// options to control how MicroPython is built
#ifndef MICROPY_VFS
-#define MICROPY_VFS (1)
+#define MICROPY_VFS (0)
#endif
#define MICROPY_VFS_FAT (MICROPY_VFS)
#define MICROPY_ALLOC_PATH_MAX (512)
