mtd: inftl.h: fix spacing errors

Replaced some spaces with tabs to fit CodingStyle guidelines

Signed-off-by: Brian Norris <norris@broadcom.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>