gpu: nvgpu: cleanup of dbg_gpu_gk20a

This change contains a generic cleanup of linux dependent parts of the
dbg_gpu_gk20a.* files. The following changes have been made

1) Moving methods into ioctl_dbg.* inside common/linux/
2) The structures dbg_session_gk20a and dbg_session_channel_data have
been split into two parts. struct device *dev is removed from
struct dbg_session_gk20a and instead packed into struct
dbg_session_gk20a_linux alongwith dbg_session_gk20a and is moved into
ioctl_dbg. dbg_session_gk20a is now rid of any linux dependencies and
remains in dbg_gpu_gk20a. Similarly, struct file is removed from
struct dbg_session_channel_data and is now packed into struct
dbg_session_channel_data_linux alongwith dbg_session_channel_data and
is moved into ioctl_dbg. struct dbg_session_channel_data is now rid of
linux dependencies and remains in dbg_gpu_gk20a.
3) A callback function is added in order to release the
dbg_session_channel_data.

JIRA NVGPU-205

Change-Id: I853da6dfbf9a96b7cd210beb77f2304445ff7ea6
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1575191
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

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

@@ -20,6 +20,7 @@
 #include <linux/file.h>
 #include <linux/anon_inodes.h>
 #include <linux/dma-buf.h>
+#include <linux/poll.h>
 
 #include <nvgpu/semaphore.h>
 #include <nvgpu/timers.h>