msm: vidc: Clean up creation of debugfs entries

On chipsets where there can be multiple video cores, when setting up the
debugfs entries for the secondary cores, several debugfs_create_files
often fail because the driver attempts to create new entries with the same
file names.

This commit moves out a lot of driver specific entries to a new function
(msm_vidc_debugfs_init_drv) that's created during driver init and during
driver probe which might be called multiple times.

Change-Id: I9fee95acbe07244c558d6ede8539dfb67e2597dc
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>