trace: convert to debugfs_file_get() and -put()

Convert the depreciated calls, debugfs_use_file_start() and
debugfs_use_file_finish() to debugfs_file_get() and debugfs_file_put()
respectively.

Change-Id: Ifdf214d4274a4062d7a077fdc94a9528d960eed6
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
Signed-off-by: Chris Lew <clew@codeaurora.org>