Revert "bpf: avoid false sharing of map refcount with max_entries"

Revert "bpf: avoid false sharing of map refcount with max_entries"

This reverts commit 5cb917aa1f1e03df9a4c29b363e3900d73508fa8 which is commit
be95a845cc4402272994ce290e3ad928aff06cb9 upstream. This commit heavily
modifies the bpf_map structure to split it on two cachelines and prevent
sharing reference counter with other, read-only fields in order to mitigate
Spectre attacks. This modification changes the ABI, so revert the mitigation
for now since the infrastructure is not yet complete for Spectre mitigation
anyway.

Gbp-Pq: Topic debian
Gbp-Pq: Name revert-bpf-avoid-false-sharing-of-map-refcount-with-.patch