Call gunzip_partial to calculate the remaining length and copy the
data to the user buffer.  This makes it shorter and reduces
duplication.
Signed-off-by: NMilton Miller <miltonm@bga.com>
Acked-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NPaul Mackerras <paulus@samba.org>