staging: ks7010: replace uint8_t with u8 in ks_wlan_set_tx_gain

In function ks_wlan_set_tx_gain a cast to uint8_t is being used
to assign transmission gain. 'tx_gain' field is defined as u8 so
replace the cast to the correct type.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>