vpu: encoder: make sure an enabled nForceIPicture flag stays enabled
vpu: encoder: make sure an enabled nForceIPicture flag stays enabled

Without this, nForceIPicture might be set to 0 even if it was 1 before,
due to the idr_interval

Signed-off-by: Carlos Rafael Giani <d7d2e6b3863b2910d2ca34828bc651c85d88df6f@pseudoterminal.org>

commshare/gstreamer-imx,commshare/gstreamer-imx,Josuercuevas/gstreamer-imx,Josuercuevas/gstreamer-imx