staging/mei: normalize prototypes of all read buffers

1. convert all read buffers to unsigned char and drop useless castings
2. simplify mei_read_slots implementation

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
4 files changed