UPSTREAM: tools/resolve_btfids: Fix warnings

* make eprintf static, used only in main.c
* initialize ret in eprintf
* remove unused *tmp

v3:
* remove another err (Song Liu)

v2:
* remove unused 'int err = -1'

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210329223143.3659983-1-sdf@google.com


(cherry picked from commit e27bfefb)
Bug: 203823368
Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: Ie1e72f161805e9b9634e45e6a348bbc386dfd076