net-sysfs: use rps_tag_ptr and remove metadata from rps_dev_flow_table

net-sysfs: use rps_tag_ptr and remove metadata from rps_dev_flow_table

Instead of storing the @log at the beginning of rps_dev_flow_table
use 5 low order bits of the rps_tag_ptr to store the log of the size.

This removes a potential cache line miss (for light traffic).

This allows us to switch to one high-order allocation instead of vmalloc()
when CONFIG_RFS_ACCEL is not set.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260302181432.1836150-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>