media: venus: vdec: Use output resolution on reconfigure

When recalculate output buffer size we have to take into account
the output resolution from the firmware received during event change
notification.

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