bpf: Free inner_map_meta when btf_record_dup fails

Whenever btf_record_dup fails, we must free inner_map_meta that was
allocated before.

This fixes a memory leak (in case of errors) during inner map creation.

Fixes: aa3496ac

 ("bpf: Refactor kptr_off_tab into btf_record")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>