Decompressors: check for write errors in decompress_unlzo.c

The return value of flush() is not checked in unlzo().  This means that
the decompressor won't stop even if the caller doesn't want more data.
This can happen e.g.  with a corrupt LZO-compressed initramfs image.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>