All FF_QSCALE_TYPE values used by libavfilter originate
from libavfilter (namely from ff_qp_table_extract());
no value is exchanged between libavcodec and libavutil.
The values that are exchanged (and used in libavfilter)
are of type enum AVVideoEncParamsType.

Therefore this patch stops using said FF_QSCALE_TYPE_*
in libavfilter and uses enum AVVideoEncParamsType
directly.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>