drm/xe/pcode: fix pcode error check

On DG2 we are now getting:

[  104.456607] xe 0000:03:00.0: [drm] *ERROR* PCODE timeout, retrying with preemption disabled

Looks like we just need to invert the error check for
xe_pcode_try_request(), which returns zero on success.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_pcode.c

@@ -155,7 +155,7 @@ int xe_pcode_request(struct xe_gt *gt, u32 mbox, u32 request,
 
 	ret = xe_pcode_try_request(gt, mbox, request, reply_mask, reply, &status,
 				   false, timeout_base_ms * 1000);
-	if (ret)
+	if (!ret)
 		goto out;
 
 	/*