staging: ks7010: change local variable type in ks7010_sdio_init_irqs

Local variable 'byte' in ks7010_sdio_init_irqs is declared as
unsigned char and can be declared as u8 which is preferred.
It is being used in calls to ks7010_sdio_writeb which is already
expected an u8.

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