tty: clearify structure initializer in notify_write()

Even though this is valid C we should not mix C99 initializers with
obfuscated ANSI C. Stick to C99 and initialize c by its name.

Found by clang:
drivers/tty/vt/vt.c:262:55: warning: explicitly assigning a variable of
type 'unsigned int' to itself [-Wself-assign]
    struct vt_notifier_param param = { .vc = vc, unicode = unicode };
                                                 ~~~~~~~ ^ ~~~~~~~

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>