media: venus: core.h: update kerneldoc

Document missing fields. This resolves two warnings:

drivers/media/platform/qcom/venus/core.h:226: warning: Function parameter or member 'venus_ver' not described in 'venus_core'
drivers/media/platform/qcom/venus/core.h:501: warning: Function parameter or member 'enc_state' not described in 'venus_inst'

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Dikshita Agarwal <quic_dikshita@quicinc.com>