net: cls_api: remove unneeded local variable in tc_dump_chain()

make clang-analyzer on x86_64 defconfig caught my attention with:

net/sched/cls_api.c:2964:3: warning: Value stored to 'parent' is never read
  [clang-analyzer-deadcode.DeadStores]
                parent = 0;
                ^

net/sched/cls_api.c:2977:4: warning: Value stored to 'parent' is never read
  [clang-analyzer-deadcode.DeadStores]
                        parent = q->handle;
                        ^

Commit 32a4f5ec

 ("net: sched: introduce chain object to uapi")
introduced tc_dump_chain() and this initial implementation already
contained these unneeded dead stores.

Simplify the code to make clang-analyzer happy.

As compilers will detect these unneeded assignments and optimize this
anyway, the resulting binary is identical before and after this change.

No functional change. No change in object code.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20201028113533.26160-1-lukas.bulwahn@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>