[Solaris] Swap output wrong on some OS versions

[jomann09]

Platform

• Solaris 11.4
• psutil 5.7.3
• Any version

Bug description
It looks like on Solaris 11.4 the output of the swap command can have an "encrypted" column.

$ /usr/sbin/swap -l
swapfile                 dev            swaplo      blocks        free encrypted
/dev/zvol/dsk/rpool/swap 303,5               0     8388608     7072944      yes

which is likely causing an issue with this line here: https://github.com/giampaolo/psutil/blob/master/psutil/_pssunos.py#L158 and may be able to be remedied by using line[3:4] instead of line[-2:]

[giampaolo]

Please make a PR.

[jomann09]

Alright added a PR for it.