Decompressors: check for write errors in decompress_unlzma.c

Decompressors: check for write errors in decompress_unlzma.c

The return value of wr->flush() is not checked in write_byte().  This
means that the decompressor won't stop even if the caller doesn't want
more data.  This can happen e.g.  with corrupt LZMA-compressed initramfs.
Returning the error quickly allows the user to see the error message
quicker.

There is a similar missing check for wr.flush() near the end of unlzma().

Signed-off-by: Lasse Collin <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Alain Knaff <[email protected]>
Cc: Albin Tonnerre <[email protected]>
Cc: Phillip Lougher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>