staging: wilc1000: removes unnecessary variable of wilc_mac_cfg_t structure

This patch removes unnecessary variable of wilc_mac_cfg_t structure.
The variable is debug print function pointer.
Removes all what used this variable.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>