bpf: Call kfree(obj) only once in free_one()

A kfree() call is always used at the end of this function implementation.
Thus specify such a function call only once instead of duplicating it
in a previous if branch.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/08987123-668c-40f3-a8ee-c3038d94f069@web.de


Signed-off-by: Alexei Starovoitov <ast@kernel.org>