Merge branch 'clean-up bpftool from legacy support'

Merge branch 'clean-up bpftool from legacy support'

Sahid Orentino Ferdjaoui says:

====================

As part of commit 93b8952d223a ("libbpf: deprecate legacy BPF map
definitions") and commit bd054102a8c7 ("libbpf: enforce strict libbpf
1.0 behaviors") The --legacy option is not relevant anymore. #1 is
removing it. #4 is cleaning the code from using libbpf_get_error().

About patches #2 and #3 They are changes discovered while working on
this series (credits to Quentin Monnet). #2 is cleaning-up usage of an
unnecessary PTR_ERR(NULL), finally #3 is fixing an invalid value
passed to strerror().

v1 -> v2:
   - Addressed review comments from Yonghong Song on patch #4
   - Added a patch #5 that removes unwanted function noticed by
     Yonghong Song
v2 -> v3
   - Addressed review comments from Andrii Nakryiko on patch #2, #3, #4
     * clean-up usage of libbpf_get_error() (#2, #3)
     * fix possible return of an uninitialized local variable err
     * fix returned errors using errno
v3 -> v4
   - Addressed review comments from Quentin Monnet
     * fix line moved from patch #2 to patch #3
     * fix missing returned errors using errno
     * fix some returned values to errno instead of -1
====================

Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>