staging: wilc1000: remove unnecessary local variables

Remove unnecessary local variable "ret" and its assignments from
functions wilc_set_tx_power and wilc_get_tx_power. Suggested by
Coccinelle.

Signed-off-by: Himadri Pandya <himadri18.07@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>