staging: ks7010: change local variable type in ks7010_rw_function

Local variable 'byte' in ks7010_rw_function is declared as unsigned
char and can be declared as u8 which is preferred. It is being used
in ks7010_sdio_readb which is already expecting an u8.

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