bpf: Avoid unnecessary use of comma operator in verifier

Although it does not seem to have any untoward side-effects, the use
of ';' to separate to assignments seems more appropriate than ','.

Flagged by clang-17 -Wcomma

No functional change intended. Compile tested only.

Signed-off-by: Simon Horman <horms@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/bpf/20231221-bpf-verifier-comma-v1-1-cde2530912e9@kernel.org