staging: ft1000: change hdr_checksum() header to one line comment in ft1000_download.c

As per coding style,C99 comments are not allowed
also, the formal header contained empty space and
redundant information that's right there in the function

Signed-off-by: Kelley Nielsen <kelleynnn@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>