drm/vkms: Update pixels accessor to support packed and multi-plane formats.

Introduce the usage of block_h/block_w to compute the offset and the
pointer of a pixel. The previous implementation was specialized for
planes with block_h == block_w == 1. To avoid confusion and allow easier
implementation of tiled formats. It also remove the usage of the
deprecated format field `cpp`.

Introduce the plane_index parameter to get an offset/pointer on a
different plane.

Acked-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241118-yuv-v14-5-2dbc2f1e222c@bootlin.com


Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>