net: filter: Avoid shadowing variable in bpf_convert_ctx_access()

Rename the local variable 'off' to 'offset' to avoid shadowing the existing
'off' variable that is declared as an `int` in the outer scope of
bpf_convert_ctx_access().

This fixes a compiler warning:

 net/core/filter.c:9679:8: warning: declaration shadows a local variable [-Wshadow]

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://patch.msgid.link/20250228-fix_filter-v1-1-ce13eae66fe9@debian.org


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