gpu: nvgpu: move cycle state buffer handler to linux

We use dma_buf pointer cyclestate_buffer_handler in common code
But since this is linux specific, we need to move this out of common code and
into linux specific code

Move dma_buf pointer cyclestate_buffer_handler from common channel code to
struct nvgpu_channel_linux

Fix all pointer accesses to this handle

Move gk20a_channel_free_cycle_stats_buffer() to ioctl_channel.c since it is
mostly linux specific
And since gk20a_channel_free_cycle_stats_buffer() needs to be called while
closing the channel, call it from nvgpu_channel_close_linux()

Jira NVGPU-397
Jira NVGPU-415

Change-Id: Ifb429e49b8f7a1c9e2bc757f3efdd50b28ceca1f
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1603909
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/common/linux/channel.c

@@ -245,6 +245,7 @@ static void nvgpu_channel_close_linux(struct channel_gk20a *ch)
 	nvgpu_channel_work_completion_clear(ch);
 
 #if defined(CONFIG_GK20A_CYCLE_STATS)
+	gk20a_channel_free_cycle_stats_buffer(ch);
 	gk20a_channel_free_cycle_stats_snapshot(ch);
 #endif
 }