inflate_fast() can do either POST INC or PRE INC on its pointers walking
the memory to decompress.  Default is PRE INC.

The sout pointer offset was miscalculated in one case as the calculation
assumed sout was a char * This breaks inflate_fast() iff configured to do
POST INC.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>