I noticed this variable used for register reads wasn't an unsigned
so this patch corrects that.  I don't believe this was causing any
issue as is but this is more consistent with the rest of the driver.
Signed-off-by: NDon Skidmore <donald.c.skidmore@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>