gpu: nvgpu: error handling for invalid ioctl call

NVGPU_GPU_IOCTL_GET_EVENT_FD should return -EINVAL when invoked in any
chips which donot have NVGPU_SUPPORT_DEVICE_EVENTS enabled. This is
resulting in an use-after-free error in UBSAN from syzkaller fuzzing
in the nvgpu driver.

Also, as an addon remove the flag clk_arb_events_supported as the
device events check can be made using the flag
NVGPU_SUPPORT_DEVICE_EVENTS.

Bug 200463292

Change-Id: I0ed0217704daa9e401b57a268a30b9f798928e4a
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1956070
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-misra-checker <svc-misra-checker@nvidia.com>
Reviewed-by: Konsta Holtta <kholtta@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c

@@ -1348,6 +1348,9 @@ static int nvgpu_gpu_get_event_fd(struct gk20a *g,
 
 	nvgpu_log_fn(g, " ");
 
+	if (!nvgpu_is_enabled(g, NVGPU_SUPPORT_DEVICE_EVENTS))
+		return -EINVAL;
+
 	if (!session)
 		return -EINVAL;