drm/vc4: hvs/v3d: Fix null dereference in unbind

drm/vc4: hvs/v3d: Fix null dereference in unbind

The hvs and v3d drivers use dev_get_drvdata(master) in their unbind
functions. Since the vc4-drm gets removed before its dependent drivers
(vc4_hvs/vc4_v3d) the vc4_hvs_unbind/vc4_v3d_unbind functions try to
get drvdata of its master and fails with a null dereference error.

Use the data pointer passed to the unbind functions directly instead of
dev_get_drvdata(master). This avoids using potentially freed memory.

Fixes: d3f5168a0810 ("drm/vc4: Bind and initialize the V3D engine.")
Fixes: c8b75bca92cb ("drm/vc4: Add KMS support for Raspberry Pi.")
Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
Link: https://patch.msgid.link/20260721-rpi-vc4-fix-v2-1-b813dcd01dc7@linutronix.de
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>