V4L/DVB (11913): cx231xx: TRY_FMT should not actually set anything

V4L/DVB (11913): cx231xx: TRY_FMT should not actually set anything

In the TRY_FMT handler the function get_scale() is called to find what the
scaler hardware will produce for a requested size.

The problem is that get_scale(struct cx231xx *dev, ..., unsigned int *vscale,
unsigned int *hscale) saves the calculated scale values into both the
pointer arguments and into dev's hscale and vscale fields.  TRY_FMT shouldn't
actually change anything in the device state.

The code to in get_scale() that writes to dev->[hv]scale can just be
deleted.  In all cases when dev's fields should be modified, get_scale()
was called with get_scale(dev, ..., &dev->hscale, &dev->vscale), so dev was
getting updated anyway.

This didn't actually cause a problem because nothing ever actually made use
of the hscale and vscale fields.  I changed cx231xx_resolution_set() to use
those fields rather than re-calculate them with a call to get_scale().

Updating [hv]scale in cx231xx_resolution_set() isn't necessary because
every call of cx231xx_resolution_set() was already preceded by a call to
get_scale() or setting the [hv]scale fields, so they will be always be
up-to-date w.r.t. width and height.

Removing the call to get_scale() from cx231xx_resolution_set() allowed
making get_scale() a static function, which is a good thing for something
with such a short name.  There is already another function with the same
name in the em28xx driver, but that one is static.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>