staging: cxt1e1: remove redundant memset() call

The banner array doens't need to set to 0.
sprintf() adds a terminating '\0'.

And the sn array can be declared and initialized to zero.
So remove redundant memset() with zero.

Remove unnecessary cast for memcpy().

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>