Revert "drm/xe: make gt_remove use devm"

This reverts commit cd506a33.

The gt_remove function was explicitly added as part of the remove flow
instead of using drmm/devm automatic cleanup due to it being illegal
to remove a component after the driver has been detached from the pci
device; the GSC proxy component is removed as part of gt_remove, so we
need to do it in the pci cleanup flow. The function already has a
comment above it to explain this.

Note that the change to use the devm also caused an invalid pointer
deref in the gsc_proxy unbind function, but I didn't bother to debug
which pointer was bad since we shouldn't be calling the unbind that
late anyway and this revert fixes it.

Both issue were not seen in CI because the GSC loading is temporarily
disabled due to a critical bug, which means we're not binding the
component.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240528182354.1200424-1-daniele.ceraolospurio@intel.com