alpha: kernel: typo issue, using '1' instead of '11'

For sending message:

        *(unsigned int *)&cpu->ipc_buffer[0] = len;
        cp1 = (char *) &cpu->ipc_buffer[1];

But for receive message:

                cnt = cpu->ipc_buffer[0] >> 32;
                ...
                       cp1 = (char *) &cpu->ipc_buffer[11];

They are not pairs, it is typo issue of the redundency '1'.

So need use '1' instead of '11'.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Chen Gang <gang.chen@asianux.com>