lib/lz4/lz4_decompress.c: document deliberate use of `&'

This operation was intentional, but tools such as smatch will warn that it
might not have been.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Yann Collet <cyan@fb.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Gao Xiang <hsiangkao@aol.com>
Link: http://lkml.kernel.org/r/3bf931c6ea0cae3e23f3485801986859851b4f04.camel@perches.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>