USB: sisusbvga: change char to u8 for sisusb_copy_memory

sisusb_copy_memory is called in several places.

sisusb_copy_memory calls sisusb_write_mem_bulk which
is called by sisusb_write and sisusb_send_bulk_msg.

change the related parameters from char to u8 accordingly

Signed-off-by: Changming Liu <liu.changm@northeastern.edu>
Link: https://lore.kernel.org/r/20200530014820.9967-2-liu.changm@northeastern.edu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>