staging: wilc1000: rename pu8bssid in wilc_set_join_req

This patch renames pu8bssid to bssid to remove pu8 prefix.
There is no need to add this prefix in order to show data type of this
variable.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>