drm/xe: Disallow input fences on zero batch execs and zero binds

drm/xe: Disallow input fences on zero batch execs and zero binds

Prevent input fences from being installed on zero batch execs or zero
binds, which were originally added to support queue idling in Mesa via
output fences. Although input fence support was introduced for interface
consistency, it leads to incorrect behavior due to chained composite
fences, which are disallowed.

Avoid the complexity of fixing this by removing support, as input fences
for these cases are not used in practice.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20251031234050.3043507-6-matthew.brost@intel.com