egl: drop memset(0) of calloc'ed memory

`_EGLDriver *drv` is a freshly calloc()'ed object, memset(0)'ing some of
it is a no-op.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/egl/main/eglfallbacks.c

@@ -49,8 +49,6 @@ _eglReturnFalse(void)
 void
 _eglInitDriverFallbacks(_EGLDriver *drv)
 {
-   memset(&drv->API, 0, sizeof(drv->API));
-
    /* the driver has to implement these */
    drv->API.Initialize = NULL;
    drv->API.Terminate = NULL;