media: venus: vdec: Make decoder return LAST flag for sufficient event

This makes the decoder to behaives equally for sufficient and
insufficient events. After this change the LAST buffer flag will be set
when the new resolution (in dynamic-resolution-change state) is smaller
then the old bitstream resolution.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>