media: venus: venc: Fix framerate/frameinterval

Venus encoder driver reports supported frame intervals values as
FRAMERATE_FACTOR multiple. The frame interval numerator and
denominator need to be reported in the same way.

With current driver, the following values are reported:
FRAME_FACTOR = 65535
min-frameinterval = 65535 / 120
max-frameinterval = 65535 / 1

This causes userspace application (e.g gstreamer) failures because
of the wrong frame interval limits. Fix that.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>