When scaler is to be used we need to make sure that the input and
output frame size do not exceed the maximum frame sizes that the
scaler h/w can handle otherwise streaming stall as the scaler
cannot proceed.

The scaler buffer is limited to 2047 pixels (i.e. 11 bits) when
attempting anything larger (2048 for example) the scaler stalls.

Realistically in an mem2mem device we can only check for this type
of issue when start_streaming is called. We can't do it during the
try_fmt/s_fmt because we do not have all of the info needed at that
point. So instead when start_streaming is called we need to check
that the input and output frames size do not exceed the scaler's
capability. The only time larger frame size are allowed is when
the input frame szie is the same as the output frame size.

Now in the case where we need to fail, start_streaming must return
all previously queued buffer back otherwise the vb2 framework
will issue kernel WARN messages.
In this case we also give an error message.
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>