binder: use kstrdup() in binderfs_binder_device_create()

In 'binderfs_binder_device_create()', use 'kstrdup()' to copy the
newly created device's name, thus making the former a bit simpler.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: "Tiffany Y. Yang" <ynaffit@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250626073054.7706-1-dmantipov@yandex.ru


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>