unzip: return uncompressed size in `filesize', and print it.

The unzip command did not provide a way for the caller to get any
information about the uncompressed size.  To make it better usable in
scripts, we now store the uncompressed size in the `filesize'
variable, like we do when for example loading a file over the network
or when reading it from a file system.  Following that analogy, it is
only consequent to also print the size.

Signed-off-by: Wolfgang Denk <wd@denx.de>