msm: vidc: Fix downscaling support check

* Update scaling ratio check to use multiplication
  instead of division as precision is lost during
  integer division
* Update upscale ratio check to ratio of output to
  input w/h as ratio of input to output w/h will be
  0 in case of upscaling

Change-Id: Icee83c8cad4ae06517c32a52b506749630ae9006
Signed-off-by: Surajit Podder <spodder@codeaurora.org>