Commit 1dce6264 introduced a regression
spotted on several G94 (FDObz #85160). This device seems to expect the
vblank period to be set after setting scale instead of before.

V2: shove this in a separate function

This is a candidate bug-fix for 3.18
Signed-off-by: NRoy Spliet <rspliet@eclipso.eu>
Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
Tested-by: NMichael Riesch <michael@riesch.at>
Tested-by: N"poma" <pomidorabelisima@gmail.com>
Tested-by: NAdam Williamson <adamw@happyassassin.net>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>