procfs and buffer calculation

[Santhosh Raju <fox%netbsd.org@localhost>]

Hello

I was recently working on making sysutils/py-psutil to be independent
of procfs being mounted, as part of a question raised in the PR[1], I
came across the buffers count implementation in procfs
- https://github.com/NetBSD/src/blob/trunk/sys/miscfs/procfs/procfs_linux.c#L203

And it looks like the value passed in should be filepg and not freepg

Line 195, shows filepg is what is being passed into buffers when
printing the stats out horizontally.

Here is an example output

$ cat /proc/meminfo
        total:    used:    free:  shared: buffers: cached:
Mem:  8301424640 8194068480 107356160        0 1378316288 7050772480
Swap: 4294926336 3880894464 414031872
MemTotal:   8106860 kB
MemFree:     104840 kB
MemShared:        0 kB
Buffers:     104840 kB
Cached:     6885520 kB
SwapTotal:  4194264 kB
SwapFree:    404328 kB

Happy to make the change and do the commit, if there are no objections to it.

Reference
1. https://github.com/giampaolo/psutil/pull/2805#discussion_r3048247572

Regards
Santhosh