lib/zlib: unpoison DFLTCC output buffers

The constraints of the DFLTCC inline assembly are not precise: they do not
communicate the size of the output buffers to the compiler, so it cannot
automatically instrument it.

Add the manual kmsan_unpoison_memory() calls for the output buffers.  The
logic is the same as in [1].

[1] 1f5ddcc009

Link: https://lkml.kernel.org/r/20240621113706.315500-21-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/zlib_dfltcc/dfltcc.h

@@ -80,6 +80,7 @@ struct dfltcc_param_v0 {
     uint8_t csb[1152];
 };
 
+static_assert(offsetof(struct dfltcc_param_v0, csb) == 384);
 static_assert(sizeof(struct dfltcc_param_v0) == 1536);
 
 #define CVT_CRC32 0