et/egl: Remove dead code.

proc_name cannot be NULL after the switch statement. proc_name is
assigned a value or the function has already returned.

src/gallium/state_trackers/egl/common/egl_g3d_st.c

@@ -71,9 +71,6 @@ egl_g3d_create_st_api(enum st_api_type api)
       return NULL;
    }
 
-   if (!proc_name)
-      return NULL;
-
    lib = util_dl_open(NULL);
    if (lib) {
       proc = util_dl_get_proc_address(lib, proc_name);