staging: unisys: visorbus: make two functions static

The functions sig_queue_offset and sig_data_offset are local to
the source and do not need to be in global scope, so make them
static.

Cleans up sparse warnings:
symbol 'sig_queue_offset' was not declared. Should it be static?
symbol 'sig_data_offset' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>