staging: ks7010: change uint8_t casts to u8 in ks_wlan_set_rate

There are some casts to uint8_t in ks_wlan_set_rate function to
assign values of the bitrate. Just change it to u8 which is the one
defined for the field 'body' of the struct which is in use.

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