bpf: Fix early return in map_check_btf

Instead of returning directly with -EOPNOTSUPP for the timer case, we
need to free the btf_record before returning to userspace.

Fixes: db559117

 ("bpf: Consolidate spin_lock, timer management into btf_record")
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>