Input: serio_raw - remove BKL

serio_raw open function already uses a mutex. Also change formatting
a bit.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>