staging: ks7010: replace unsigned char type with u8

Variable 'byte' in ks7010_upload_firmware function is declared
as unsigned char and is only being used to read hardware
registers which are expected in sdio_read_byteb function as u8.
Change 'byte' variable type to u8 which is preferred.

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