drm/i915: move intel_gvt_init() level higher

drm/i915: move intel_gvt_init() level higher

Both initialisation and removal of GVT happen at different abstraction
levels. Hence caller of i915_driver_hw_probe() has no way of knowing
status of intel_gvt_init(). This can lead to an unbalanced number of
calls of intel_gvt_init() and intel_gvt_driver_remove() since GVT error
path is currently handled in i915_driver_probe(). One such scenario has
been seen with i915_driver_hw_probe() fault injection, which caused
double entry deletion and list corruption.

Move intel_gvt_init() up to i915_driver_probe(). Add out_cleanup_gvt
error path for removing gvt. Trigger it only after intel_gvt_init()
succeeded.

In case intel_gvt_init() failed, theoretically we should follow err_msi
error path. That is actually impossible since call to intel_gvt_init()
unconditionally returns 0, although it claims to return negative error
code on failure. Thus follow standard out_cleanup_hw error path on a
hypothetical future intel_gvt_init() failure. Remove err_msi label from
i915_driver_hw_probe() since intel_gvt_init() was the only user of it.

Changelog:
v1->v2
- don't move err_msi error path from i915_driver_hw_probe (Jani)
- rewrite commit message

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15481
Signed-off-by: Michał Grzelak <michal.grzelak@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patch.msgid.link/20260129090129.2601661-2-michal.grzelak@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>