[media] mtk-vcodec: fix two compiler warnings

mtk-vcodec/mtk_vcodec_enc.c: In function 'mtk_venc_worker':
mtk-vcodec/mtk_vcodec_enc.c:1030:43: warning: format '%lx' expects argument of type 'long unsigned int', but argument 7 has type 'size_t {aka unsigned int}' [-Wformat=]
mtk-vcodec/mtk_vcodec_enc.c:1030:43: warning: format '%lx' expects argument of type 'long unsigned int', but argument 10 has type 'size_t {aka unsigned int}' [-Wformat=]

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>