tty/serial: digicolor: Fix digicolor-usart already registered warning
When modprobe/rmmod/modprobe module, if platform_driver_register() fails,
the kernel complained,
proc_dir_entry 'driver/digicolor-usart' already registered
WARNING: CPU: 1 PID: 5636 at fs/proc/generic.c:360 proc_register+0x19d/0x270
Fix this by adding uart_unregister_driver() when platform_driver_register() fails.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>