Drmm actions are not the right ones to clean up BOs and we should use
devm instead. However, we can also instead just allocate the objects
using the managed_bo function, which will internally register the
correct cleanup call and therefore allows us to simplify the code.

While at it, switch to drmm_kzalloc for the GSC proxy allocation to
further simplify the cleanup.

Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240815230541.3828206-1-lucas.demarchi@intel.comSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>