libsparse: output_file.c, fix large data chunk issue

CHUNK_HEADER structure type allows DATA chunk to be up to MAX_UINT
large.

The write() callback LEN parameter should be unsigned int.

Also:
- write() callback should continue to write data if less than expected
  data have been written.
- gzerror() returns LEN on success, 0 otherwise

Test: manual
Change-Id: Id46d664b84c1a506f419524fe28055f784c2ae7a
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>