lib/zlib: remove redundation assignement of avail_in dfltcc_gdht()

cppcheck reports
lib/zlib_dfltcc/dfltcc_deflate.c:65:21: warning: Redundant assignment of 'avail_in' to itself. [selfAssignment]
    size_t avail_in = avail_in = strm->avail_in;

Only setting avail_in once is needed.

Link: https://lkml.kernel.org/r/20230128165048.1245792-1-trix@redhat.com
Fixes: aa5b395 ("lib/zlib: add s390 hardware support for kernel zlib_deflate")
Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Tom Rix

lib/zlib_dfltcc/dfltcc_deflate.c

@@ -62,7 +62,7 @@ static void dfltcc_gdht(
 {
     deflate_state *state = (deflate_state *)strm->state;
     struct dfltcc_param_v0 *param = &GET_DFLTCC_STATE(state)->param;
-    size_t avail_in = avail_in = strm->avail_in;
+    size_t avail_in = strm->avail_in;
 
     dfltcc(DFLTCC_GDHT,
            param, NULL, NULL,