media: venus: hfi_cmds: struct hfi_session_release_buffer_pkt: Replace 1-element array with flexible array

Replace the deprecated[1] use of a 1-element array in
struct hfi_session_release_buffer_pkt with a modern flexible array.

No binary differences are present after this conversion.

Link: https://github.com/KSPP/linux/issues/79 [1]
Reviewed-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Acked-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20240710230914.3156277-1-kees@kernel.orgSigned-off-by: Kees Cook <kees@kernel.org>