drm/xe/lrc: Allow INDIRECT_CTX for more engine classes

Currently it's only allowed for render and compute. Going forward we
want to enable it for more engine classes. Let the XE_LRC_FLAG_INDIRECT_CTX
flag (and thus gt_engine_needs_indirect_ctx()) be the deciding factor
for its availability.

While at it, add the missing const to rcs_funcs array. Since
CTX_INDIRECT_CTX_OFFSET_DEFAULT already matches the HW default and
gt_engine_needs_indirect_ctx() only ever enables it for rcs/ccs, there
is no change in behavior, it's only preparation for future use case.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250916-wa-bb-cmds-v5-5-306bddbc15da@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>