drm/xe/guc: Handle regset overflow check for entire GT

Checking whether a single engine's register save/restore entries
overflow the expected/pre-allocated GuC ADS regset area isn't terribly
useful; we actually want to check whether the combined entries from all
engines on the GT overflow the regset space.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230308005509.2975663-1-matthew.d.roper@intel.com


Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>