I wasn't able to find a way to do this with the CLI natively, but if you don't mind PowerShell, it should be fairly easy to get the output you want.
# Open connection to NetApp controller
Connect-NcController <controller hostname>
# Run SSH command and store output as variable named $autostate
$autostate = Invoke-NcSsh -Command "set d; y; vol efficiency status -vserver EU51SVMP016 -volume * -l"
# Output is a multi-line string stored as one large string, so we'll split it into multiple strings delimited by a new line
$autostate = $autostate -split "`n"
# Now we can select the strings we want for the output. I've selected the "Path" and "Auto State" strings
$autostate | Select-String -Pattern "Auto State","Path"
Output looks like this:
Path: /vol/path1
Auto State: -
Path: /vol/path2
Auto State: -
Path: /vol/path3
Auto State: -
Path: /vol/path4
Auto State: -
Path: /vol/path5
Auto State:
Not pretty, but it works!