uapi: the feature core_ffi_c is now stable

* The feature `core_ffi_c` feature is now stable since rust 1.64.0 and
no longer requires an attribute to enable.

Signed-off-by: Andy-Python-Programmer <andypythonappdeveloper@gmail.com>

Author: Andy-Python-Programmer

src/uapi/src/lib.rs

@@ -1,4 +1,3 @@
-#![feature(core_ffi_c)]
 #![no_std]
 
 pub mod drm;