As of v2.1.0, falcon_decode_var() contains a quirk to fix a rounding
error, as explained by Günther Kelleter on Fri, 30 Aug 1996:
This diff removes the now obsolete Falcon video option "pwrsave", and
fixes a rounding error that is triggered by the resolution switching X
server (those who use the pixel clock value 39722 in their /etc/fb.modes
should change it to 39721).
However, this causes the modified video mode returned by
falcon_decode_var() to not match the video mode returned by
falcon_encode_var(). Fix this by dropping the quirk.
Unfortunately /etc/fb.modes in fbset was never updated, so the
"640x480-60" mode still contains the wrong pixclock.
Hence this change may introduce a regression.