media: renesas: vsp1: hsit: Fix size enumeration

media: renesas: vsp1: hsit: Fix size enumeration

The HSIT entity performs format conversion, which leads to incorrect
results with the vsp1_subdev_enum_frame_size() helper. Implement a
custom .enum_frame_size() handler that correctly validates the media bus
code. Size validation is identical to the helper.

Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> # HiHope RZ/G2M
Link: https://patch.msgid.link/20260318235907.831556-9-laurent.pinchart+renesas@ideasonboard.com
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>