staging: ks7010: change local variable type in _ks_wlan_hw_power_save

Local variable 'byte' in _ks_wlan_hw_power_save function is declared
as unsigned char and can be declared as u8 which is preferred. It
is being using with ks7010_sdio_readb which expects u8 already.

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